Patent Publication Number: US-11661625-B2

Title: Primers for immune repertoire profiling

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 63/025,079, filed May 14, 2020, the content of this related application is incorporated herein by reference in its entirety for all purposes. 
    
    
     REFERENCE TO SEQUENCE LISTING 
     The present application is being filed along with a Sequence Listing in electronic format. The Sequence Listing is provided as a file entitled 68EB_298732_US, created May 11, 2021, which is 12.0 kilobytes in size. The information in the electronic format of the Sequence Listing is incorporated herein by reference in its entirety. 
     BACKGROUND 
     Field 
     The present disclosure relates generally to the field of molecular biology, and for particular to multiomics analyses using molecular barcoding. 
     Description of the Related Art 
     Methods and techniques of molecular barcoding are useful for single cell transcriptomics analysis, including deciphering gene expression profiles to determine the states of cells using, for example, reverse transcription, polymerase chain reaction (PCR) amplification, and next generation sequencing (NGS). Molecular barcoding is also useful for single cell proteomics analysis. There is a need for methods and compositions (e.g., primer panels) for the determination of the nucleotide sequence of the complete variable region of nucleic acids encoding BCR and TCR immune receptor polypeptides in high-throughput sequencing single cell multiomics assays. 
     SUMMARY 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 10-17; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 18-20. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more first primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more first primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 10-17; one or more first primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more first primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 18-20; one or more second primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more second primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. 
     In some embodiments, the immunoglobulin light chain comprises a kappa chain and/or a lambda chain. In some embodiments, the constant domain of an immunoglobulin heavy chain comprises Immunoglobulin Heavy Constant Alpha (IGHA), Immunoglobulin Heavy Constant Delta (IGHD), Immunoglobulin Heavy Constant Epsilon (IGRE), Immunoglobulin Heavy Constant Gamma (IGHG), Immunoglobulin Heavy Constant Mu (IGHM), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin heavy chain comprises Immunoglobulin Heavy Constant Gamma 1 (IGHG1), Immunoglobulin Heavy Constant Gamma 2A (IGHG2A), Immunoglobulin Heavy Constant Gamma 2C (IGHG2C), Immunoglobulin Heavy Constant Gamma 2B (IGHG2B), Immunoglobulin Heavy Constant Gamma 3 (IGHG3), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin light chain comprises Immunoglobulin Kappa Constant (IGKC), Immunoglobulin Lambda Constant (IGLC), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin light chain comprises Immunoglobulin Lambda Constant 1 (IGLC1), Immunoglobulin Lambda Constant 2 (IGLC2), Immunoglobulin Lambda Constant 3 (IGLC3), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin heavy chain comprises the constant domain of a mouse immunoglobulin heavy chain, and wherein the constant domain of an immunoglobulin light chain comprises the constant domain of a mouse immunoglobulin light chain. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 1; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 2; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 3; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 4. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 1; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 2; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 3; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 4; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. 
     In some embodiments, the constant domain of the T Cell Receptor Gamma Chain comprises T Cell Receptor Gamma Constant 1 (TRGC1), T Cell Receptor Gamma Constant 2 (TRGC2), T Cell Receptor Gamma Constant 4 (TRGC4), or any combination thereof. In some embodiments, the constant domain of a T Cell Receptor Alpha Chain comprises T Cell Receptor Alpha Constant (TRAC). In some embodiments, the constant domain of a T Cell Receptor Beta Chain comprises T Cell Receptor Beta Constant (TRBC). In some embodiments, the constant domain of a T Cell Receptor Delta Chain comprises T Cell Receptor Delta Constant (TRDC). In some embodiments, the constant domain of a T Cell Receptor Alpha Chain comprises the constant domain of a mouse T Cell Receptor Alpha Chain, wherein the constant domain of a T Cell Receptor Beta Chain comprises the constant domain of a mouse T Cell Receptor Beta Chain, wherein the constant domain of a T Cell Receptor Gamma Chain comprises the constant domain of a mouse T Cell Receptor Gamma Chain, and wherein the constant domain of a T Cell Receptor Delta Chain comprises the constant domain of a mouse T Cell Receptor Delta Chain. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of an immunoglobulin heavy chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. In some embodiments, said probe or primer comprises a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of an immunoglobulin light chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. In some embodiments, said probe or primer comprises a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. In some embodiments, said probe or primer comprises a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. In some embodiments, probe or primer comprises a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. In some embodiments, said probe or primer comprises a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. In some embodiments, said probe or primer comprises a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. In some embodiments, said probe or primer consists of a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. 
     Disclosed herein include methods for labeling nucleic acid targets in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; and extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label. The method can comprise determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences, second molecular labels with distinct sequences, or a combination thereof, associated with the plurality of extended barcoded nucleic acid molecules, or products thereof. 
     Disclosed herein include methods for determining the numbers of nucleic acid targets in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label; and determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences, second molecular labels with distinct sequences, or a combination thereof, associated with the plurality of extended barcoded nucleic acid molecules, or products thereof. 
     The method can comprise amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules each comprising the first molecular label or the second molecular label, wherein determining the copy number of the nucleic acid target in the sample comprises: determining the copy number of the nucleic acid target in the sample based on the number of second molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. In some embodiments, determining the copy number of the nucleic acid target in the sample comprises: determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. The method can comprise amplifying the plurality of extended barcoded nucleic acid molecules to generate copies of the plurality of extended barcoded nucleic acid molecules, wherein determining the copy number of the nucleic acid target in the sample comprises: determining the copy number of the nucleic acid target in the sample based on (i) the number of first molecular labels with distinct sequences associated with the copies of plurality of extended barcoded nucleic acid molecules, or products thereof, and/or (ii) the number of second molecular labels with distinct sequences associated with the copies of plurality of extended barcoded nucleic acid molecules, or products thereof. 
     Disclosed herein include methods of determining the numbers of a nucleic acid target in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label; amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules each comprising the first molecular label or the second molecular label; and determining the copy number of the nucleic acid target in the sample based on the number of second molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. 
     In some embodiments, the method comprises determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. In some embodiments, the method comprises denaturing the plurality of barcoded nucleic acid molecules prior to hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules. In some embodiments, the method comprises denaturing the plurality of extended barcoded nucleic acid molecules prior to amplifying the plurality of extended barcoded nucleic acid molecules. In some embodiments, determining the copy number of the nucleic acid target comprises determining the copy number of each of the plurality of nucleic acid targets in the sample based on the number of second molecular labels with distinct sequences associated with single-labeled nucleic acid molecules of the plurality of single-labeled nucleic acid molecules comprising a sequence of the each of the plurality of nucleic acid targets. In some embodiments, determining the copy number of the nucleic acid target comprises determining the copy number of each of the plurality of nucleic acid targets in the sample based on the number of first molecular labels with distinct sequences associated with single-labeled nucleic acid molecules of the plurality of single-labeled nucleic acid molecules comprising a sequence of the each of the plurality of nucleic acid targets. In some embodiments, the sequence of the each of the plurality of nucleic acid targets comprises a subsequence of the each of the plurality of nucleic acid targets. In some embodiments, the sequence of the nucleic acid target in the plurality of barcoded nucleic acid molecules comprises a subsequence of the nucleic acid target. 
     In some embodiments, the first molecular label is hybridized to the second molecular label after extending the 3′-ends of the plurality of barcoded nucleic acid molecules. In some embodiments, the extended barcoded nucleic acid molecules each comprise the first molecular label, the second molecular label, the target-binding region, and the complement of the target-binding region. In some embodiments, the complement of the target-binding region is complementary to a portion of the target-binding region. In some embodiments, the target-binding region comprises a gene-specific sequence. In some embodiments, the target-binding region comprises a poly(dT) sequence. 
     In some embodiments, hybridizing the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of the barcoded nucleic acid molecule itself comprises intramolecular hybridization of the target-binding region and the complement of the target-binding region within a barcoded nucleic acid molecule to form a stem loop. In some embodiments, the second molecular label is the complement of the first molecular label. In some embodiments, hybridizing the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of an oligonucleotide barcode of the plurality of oligonucleotide barcodes comprises intermolecular hybridization of the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of an oligonucleotide barcode of the plurality of oligonucleotide barcodes. In some embodiments, the second molecular label is a different from the first molecular label, and wherein the second molecular label is not a complement of the first molecular label. In some embodiments, the method comprises extending the 3′ ends of the oligonucleotide barcodes hybridized to the complement of the target-binding region of the barcoded nucleic acid molecule to generate a plurality of extended barcoded nucleic acid molecules each comprising a complement of the first molecular label and a second molecular label. In some embodiments, the sequence of the second molecular label is different from the sequence of the first molecular label, wherein the wherein the second molecular label is not a complement of the first molecular label. In some embodiments, hybridizing the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules comprises intermolecular hybridization of the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules. In some embodiments, the sequence of the second molecular label is different from the sequence of the first molecular label, and wherein the second molecular label is not a complement of the first molecular label. 
     In some embodiments, the reverse transcriptase is capable of terminal transferase activity. In some embodiments, the template switch oligonucleotide comprises one or more 3′ ribonucleotides, for example three 3′ ribonucleotides. In some embodiments, the 3′ ribonucleotides comprise guanine. In some embodiments, the reverse transcriptase comprises a viral reverse transcriptase, for example a murine leukemia virus (MLV) reverse transcriptase or a Moloney murine leukemia virus (MMLV) reverse transcriptase. 
     In some embodiments, the sample comprises a single cell. In some embodiments, the sample comprises a plurality of cells, a plurality of single cells, a tissue, a tumor sample, or any combination thereof. In some embodiments, a single cell comprises an immune cell. In some embodiments, the immune cell is a B cell or a T cell. In some embodiments, a single cell comprises a circulating tumor cell. In some embodiments, each oligonucleotide barcode comprises a first universal sequence. In some embodiments, the plurality of extended barcoded nucleic acid molecules comprises a first universal sequence and a complement of the first universal sequence. In some embodiments, amplifying the plurality of extended barcoded nucleic acid molecules to generate copies of the plurality of extended barcoded nucleic acid molecules comprises using a primer capable of hybridizing to the first universal sequence, or a complement thereof. 
     In some embodiments, amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules comprises using a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more first amplification primers. In some embodiments, the one or more first amplification primers comprises: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 10-17; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 18-20. 
     In some embodiments, the one or more first amplification primers comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 1; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 2; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 3; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 4. 
     The method can comprise: amplifying the plurality of single-labeled nucleic acid molecules using primers capable of hybridizing to the first universal sequence, or a complement thereof, and one or more second amplification primers, thereby generating a first plurality of barcoded amplicons. In some embodiments, the one or more second amplification primers: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. In some embodiments, the one or more second amplification primers comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. In some embodiments, the immunoglobulin heavy chain comprises an alpha chain, a delta chain, an epsilon chain, a gamma chain, a mu chain, or any combination thereof. 
     In some embodiments, the immunoglobulin light chain comprises a kappa chain and/or a lambda chain. In some embodiments, the constant domain of an immunoglobulin heavy chain comprises Immunoglobulin Heavy Constant Alpha (IGHA), Immunoglobulin Heavy Constant Delta (IGHD), Immunoglobulin Heavy Constant Epsilon (IGRE), Immunoglobulin Heavy Constant Gamma (IGHG), Immunoglobulin Heavy Constant Mu (IGHM), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin heavy chain comprises Immunoglobulin Heavy Constant Gamma 1 (IGHG1), Immunoglobulin Heavy Constant Gamma 2A (IGHG2A), Immunoglobulin Heavy Constant Gamma 2C (IGHG2C), Immunoglobulin Heavy Constant Gamma 2B (IGHG2B), Immunoglobulin Heavy Constant Gamma 3 (IGHG3), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin light chain comprises Immunoglobulin Kappa Constant (IGKC), Immunoglobulin Lambda Constant (IGLC), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin light chain comprises Immunoglobulin Lambda Constant 1 (IGLC1), Immunoglobulin Lambda Constant 2 (IGLC2), Immunoglobulin Lambda Constant 3 (IGLC3), or any combination thereof. In some embodiments, the constant domain of an immunoglobulin heavy chain comprises the constant domain of a mouse immunoglobulin heavy chain, and wherein the constant domain of an immunoglobulin light chain comprises the constant domain of a mouse immunoglobulin light chain. 
     In some embodiments, the constant domain of the T Cell Receptor Gamma Chain comprises T Cell Receptor Gamma Constant 1 (TRGC1), T Cell Receptor Gamma Constant 2 (TRGC2), T Cell Receptor Gamma Constant 4 (TRGC4), or any combination thereof. In some embodiments, the constant domain of a T Cell Receptor Alpha Chain comprises T Cell Receptor Alpha Constant (TRAC). In some embodiments, the constant domain of a T Cell Receptor Beta Chain comprises T Cell Receptor Beta Constant (TRBC). In some embodiments, the constant domain of a T Cell Receptor Delta Chain comprises T Cell Receptor Delta Constant (TRDC). In some embodiments, the constant domain of a T Cell Receptor Alpha Chain comprises the constant domain of a mouse T Cell Receptor Alpha Chain, wherein the constant domain of a T Cell Receptor Beta Chain comprises the constant domain of a mouse T Cell Receptor Beta Chain, wherein the constant domain of a T Cell Receptor Gamma Chain comprises the constant domain of a mouse T Cell Receptor Gamma Chain, and wherein the constant domain of a T Cell Receptor Delta Chain comprises the constant domain of a mouse T Cell Receptor Delta Chain. 
     In some embodiments, the first amplification primer and/or the second amplification primer is a target-specific primer, and wherein the target-specific primer specifically hybridizes to a constant region of an immune receptor. In some embodiments, the immune receptor is a T cell receptor (TCR) and/or a B cell receptor (BCR) receptor, and optionally the TCR comprises TCR alpha chain, TCR beta chain, TCR gamma chain, TCR delta chain, or any combination thereof; and the BCR receptor comprises BCR heavy chain and/or BCR light chain. In some embodiments, extending 3′-ends of the plurality of barcoded nucleic acid molecules comprises extending 3 ‘-ends of the plurality of barcoded nucleic acid molecules using a DNA polymerase lacking at least one of 5’ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity, and optionally the DNA polymerase comprises a Klenow Fragment. The method can comprise: obtaining sequence information of the plurality of extended barcoded nucleic acid molecules, or products thereof. Obtaining the sequence information can comprise attaching sequencing adaptors to the plurality of extended barcoded nucleic acid molecules, or products thereof. Obtaining the sequence information can comprise attaching sequencing adaptors to the plurality of single-labeled nucleic acid molecules, or products thereof. Obtaining the sequence information can comprise attaching sequencing adaptors to the first plurality of barcoded amplicons, or products thereof. 
     In some embodiments, obtaining the sequence information comprises obtaining the sequence information of the BCR light chain and the BCR heavy chain of a single cell. In some embodiments, the sequence information of the BCR light chain and the BCR heavy chain comprises the sequence of the complementarity determining region 1 (CDR1), the CDR2, the CDR3, or any combination thereof, of the BCR light chain and/or the BCR heavy chain. In some embodiments, method comprises pairing the BCR light chain and the BCR heavy chain of the single cell based on the obtained sequence information. In some embodiments, the sample comprises a plurality of single cells, the method comprising pairing the BCR light chain and the BCR heavy chain of at least 50% of said single cells based on the obtained sequence information. In some embodiments, obtaining the sequence information comprises obtaining the sequence information of the TCR alpha chain and the TCR beta chain of a single cell. In some embodiments, the sequence information of the TCR alpha chain and the TCR beta chain comprises the sequence of the complementarity determining region 1 (CDR1), the CDR2, the CDR3, or any combination thereof, of the TCR alpha chain and/or the TCR beta chain. In some embodiments, the method comprises pairing the TCR alpha chain and the TCR beta chain of the single cell based on the obtained sequence information. In some embodiments, the sample comprises a plurality of single cells, the method comprising pairing the TCR alpha chain and the TCR beta chain of at least 50% of said single cells based on the obtained sequence information. In some embodiments, obtaining the sequence information comprises obtaining the sequence information of the TCR gamma chain and the TCR delta chain of a single cell. In some embodiments, the sequence information of the TCR gamma chain and the TCR delta chain comprises the sequence of the complementarity determining region 1 (CDR1), the CDR2, the CDR3, or any combination thereof, of the TCR gamma chain and/or the TCR delta chain. In some embodiments, the method comprises pairing the TCR gamma chain and the TCR delta chain of the single cell based on the obtained sequence information. In some embodiments, the sample comprises a plurality of single cells, the method comprising pairing the TCR gamma chain and the TCR delta chain of at least 50% of said single cells based on the obtained sequence information. 
     In some embodiments, the complement of the target-binding region comprises the reverse complementary sequence of the target-binding region. In some embodiments, the complement of the target-binding region comprises the complementary sequence of the target-binding region. In some embodiments, the complement of the molecular label comprises a reverse complementary sequence of the molecular label. In some embodiments, the complement of the molecular label comprises a complementary sequence of the molecular label. In some embodiments, the plurality of barcoded nucleic acid molecules comprises barcoded deoxyribonucleic acid (DNA) molecules. In some embodiments, the barcoded nucleic acid molecules comprise barcoded ribonucleic acid (RNA) molecules. In some embodiments, the nucleic acid target comprises a nucleic acid molecule. In some embodiments, the nucleic acid molecule comprises ribonucleic acid (RNA), messenger RNA (mRNA), microRNA, small interfering RNA (siRNA), RNA degradation product, RNA comprising a poly(A) tail, or any combination thereof. In some embodiments, the mRNA encodes an immune receptor. In some embodiments, the nucleic acid target comprises a cellular component binding reagent. In some embodiments, the nucleic acid molecule is associated with the cellular component binding reagent. In some embodiments, the method comprises dissociating the nucleic acid molecule and the cellular component binding reagent. In some embodiments, at least 10 of the plurality of oligonucleotide barcodes comprise different molecular label sequences. In some embodiments, each molecular label of the plurality of oligonucleotide barcodes comprises at least 6 nucleotides. 
     In some embodiments, the plurality of oligonucleotide barcodes are associated with a solid support. In some embodiments, the plurality of oligonucleotide barcodes associated with the same solid support each comprise an identical sample label. In some embodiments, each sample label of the plurality of oligonucleotide barcodes comprises at least 6 nucleotides. In some embodiments, the plurality of oligonucleotide barcodes each comprise a cell label. In some embodiments, each cell label of the plurality of oligonucleotide barcodes comprises at least 6 nucleotides. In some embodiments, oligonucleotide barcodes associated with the same solid support comprise the same cell label. In some embodiments, oligonucleotide barcodes associated with different solid supports comprise different cell labels. In some embodiments, the plurality of extended barcoded nucleic acid molecules each comprises a cell label and a complement of the cell label. In some embodiments, the complement of the cell label comprises a reverse complementary sequence of the cell label. In some embodiments, the complement of the cell label comprises a complementary sequence of the cell label. In some embodiments, the method comprising extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of one or more of ethylene glycol, polyethylene glycol, 1,2- propanediol, dimethyl sulfoxide (DMSO), glycerol, formamide, 7-deaza-GTP, acetamide, tetramethylammonium chloride salt, betaine, or any combination thereof. In some embodiments, the solid support comprises a synthetic particle. In some embodiments, the solid support comprises a planar surface. 
     In some embodiments, the sample comprises a single cell, the method comprising associating a synthetic particle comprising the plurality of the oligonucleotide barcodes with the single cell in the sample. In some embodiments, the method comprises lysing the single cell after associating the synthetic particle with the single cell. In some embodiments, lysing the single cell comprises heating the sample, contacting the sample with a detergent, changing the pH of the sample, or any combination thereof. In some embodiments, the synthetic particle and the single cell are in the same well. In some embodiments, the synthetic particle and the single cell are in the same droplet. In some embodiments, at least one of the plurality of oligonucleotide barcodes is immobilized on the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is partially immobilized on the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is enclosed in the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is partially enclosed in the synthetic particle. In some embodiments, the synthetic particle is disruptable. In some embodiments, the synthetic particle comprises a bead. In some embodiments, the bead comprises a sepharose bead, a streptavidin bead, an agarose bead, a magnetic bead, a conjugated bead, a protein A conjugated bead, a protein G conjugated bead, a protein A/G conjugated bead, a protein L conjugated bead, an oligo(dT) conjugated bead, a silica bead, a silica-like bead, an anti-biotin microbead, an anti-fluorochrome microbead, or any combination thereof. In some embodiments, the synthetic particle comprises a material selected from the group consisting of polydimethylsiloxane (PDMS), polystyrene, glass, polypropylene, agarose, gelatin, hydrogel, paramagnetic, ceramic, plastic, glass, methylstyrene, acrylic polymer, titanium, latex, sepharose, cellulose, nylon, silicone, and any combination thereof. In some embodiments, the synthetic particle comprises a disruptable hydrogel particle. In some embodiments, each of the plurality of oligonucleotide barcodes comprises a linker functional group, the synthetic particle comprises a solid support functional group, and/or the support functional group and the linker functional group are associated with each other. In some embodiments, the linker functional group and the support functional group are individually selected from the group consisting of C6, biotin, streptavidin, primary amine(s), aldehyde(s), ketone(s), and any combination thereof. 
     Disclosed herein include methods for amplifying a plurality of nucleic acid molecules. The method can comprise: contacting a plurality of nucleic acid molecules comprising a first universal sequence with a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more of the compositions disclosed herein; and amplifying the plurality of nucleic acid molecules to generate a first plurality of amplified products. The method can comprise: amplifying the first plurality of amplified products using a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more of the compositions disclosed herein, thereby generating a second plurality of amplified products. In some embodiments, one or more nucleic acid molecules comprises the sequence of: a constant domain of an immunoglobulin heavy chain and/or a constant domain of an immunoglobulin light chain. In some embodiments, one or more nucleic acid molecules comprises the sequence of: a constant domain of a T Cell Receptor Alpha Chain, a constant domain of a T Cell Receptor Beta Chain, a constant domain of a T Cell Receptor Delta Chain, a constant domain of a T Cell Receptor Gamma Chain, or any combination thereof. The method can comprise obtaining the sequence information of the first plurality of amplified products, the second plurality of amplified products, or products thereof. The plurality of nucleic acid molecules can comprise deoxyribonucleic acid (DNA) molecules and/or ribonucleic acid (RNA) molecules. 
     Disclosed herein include compositions comprising one or more of the oligonucleotide probes and/or primers disclosed herein. Disclosed herein include kits. In some embodiments, the kit comprises one or more the compositions provided herein (e.g., probes and/or primers and/or primer panels capable of hybridizing to a constant domain of an immune receptor (e.g., TCR, BCR)). In some embodiments, the kit comprises: a plurality of oligonucleotide barcodes, wherein each of the plurality of oligonucleotide barcodes comprises a molecular label and a target-binding region, and wherein at least 10 of the plurality of oligonucleotide barcodes comprise different molecular label sequences; a reverse transcriptase; a template switching oligonucleotide comprising the target-binding region, or a portion thereof; and a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity. 
     In some embodiments, the DNA polymerase comprises a Klenow Fragment. In some embodiments, the reverse transcriptase comprises a viral reverse transcriptase. In some embodiments, the viral reverse transcriptase is a murine leukemia virus (MLV) reverse transcriptase. In some embodiments, the viral reverse transcriptase is a Moloney murine leukemia virus (MMLV) reverse transcriptase. In some embodiments, the template switch oligonucleotide comprises one or more 3′ ribonucleotides. In some embodiments, the template switch oligonucleotide comprises three 3′ ribonucleotides. In some embodiments, the 3′ ribonucleotides comprise guanine. In some embodiments, the kit comprises one or more of ethylene glycol, polyethylene glycol, 1,2- propanediol, dimethyl sulfoxide (DMSO), glycerol, formamide, 7-deaza-GTP, acetamide, tetramethylammonium chloride salt, betaine, or any combination thereof. 
     In some embodiments, the kit comprises a buffer., In some embodiments, the kit comprises a cartridge. In some embodiments, the kit comprises one or more reagents for a reverse transcription reaction. In some embodiments, the kit comprises one or more reagents for an amplification reaction. In some embodiments, the target-binding region comprises a gene-specific sequence, an oligo(dT) sequence, a random multimer, or any combination thereof. In some embodiments, the oligonucleotide barcode comprises an identical sample label and/or an identical cell label In some embodiments, each sample label and/or cell label of the plurality of oligonucleotide barcodes comprise at least 6 nucleotides. In some embodiments, each molecular label of the plurality of oligonucleotide barcodes comprises at least 6 nucleotides. In some embodiments, at least one of the plurality of oligonucleotide barcodes is immobilized on the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is partially immobilized on the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is enclosed in the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is partially enclosed in the synthetic particle. In some embodiments, the synthetic particle is disruptable. In some embodiments, the synthetic particle comprises a bead. In some embodiments, the bead comprises a sepharose bead, a streptavidin bead, an agarose bead, a magnetic bead, a conjugated bead, a protein A conjugated bead, a protein G conjugated bead, a protein A/G conjugated bead, a protein L conjugated bead, an oligo(dT) conjugated bead, a silica bead, a silica-like bead, an anti-biotin microbead, an anti-fluorochrome microbead, or any combination thereof. In some embodiments, the synthetic particle comprises a material selected from the group consisting of polydimethylsiloxane (PDMS), polystyrene, glass, polypropylene, agarose, gelatin, hydrogel, paramagnetic, ceramic, plastic, glass, methylstyrene, acrylic polymer, titanium, latex, sepharose, cellulose, nylon, silicone, and any combination thereof. In some embodiments, the synthetic particle comprises a disruptable hydrogel particle. In some embodiments, each of the plurality of oligonucleotide barcodes comprises a linker functional group, the synthetic particle comprises a solid support functional group, and/or the support functional group and the linker functional group are associated with each other. In some embodiments, the linker functional group and the support functional group are individually selected from the group consisting of C6, biotin, streptavidin, primary amine(s), aldehyde(s), ketone(s), and any combination thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a non-limiting exemplary barcode. 
         FIG.  2    shows a non-limiting exemplary workflow of barcoding and digital counting. 
         FIG.  3    is a schematic illustration showing a non-limiting exemplary process for generating an indexed library of targets barcoded at the 3′-ends from a plurality of targets. 
         FIG.  4 A  and  FIG.  4 B  show a schematic illustration of a non-limiting exemplary method of gene-specific labeling nucleic acid targets on the 5′-ends. 
         FIG.  5 A  and  FIG.  5 B  show a schematic illustration of a non-limiting exemplary method of labeling nucleic acid targets on the 5′-ends for whole transcriptome analysis. 
         FIG.  6 A - FIG.  6 K  show schematic illustrations of non-limiting exemplary workflows of determining the sequences of a nucleic acid target (e.g., the V(D)J region of an immune receptor) using 5′ barcoding and/or 3′ barcoding. 
         FIG.  7    shows a non-limiting exemplary schematic illustration of performing a V(D)J protocol, an antibody-oligonucleotide (AbO) protocol, and a single cell mRNA expression profile protocol (e.g., the BD Rhapsody targeted protocol) as one workflow. 
         FIG.  8    depicts a non-limiting exemplary workflow for the generation of the primer panels disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein and made part of the disclosure herein. 
     All patents, published patent applications, other publications, and sequences from GenBank, and other databases referred to herein are incorporated by reference in their entirety with respect to the related technology. 
     Quantifying small numbers of nucleic acids, for example messenger ribonucleotide acid (mRNA) molecules, is clinically important for determining, for example, the genes that are expressed in a cell at different stages of development or under different environmental conditions. However, it can also be very challenging to determine the absolute number of nucleic acid molecules (e.g., mRNA molecules), especially when the number of molecules is very small. One method to determine the absolute number of molecules in a sample is digital polymerase chain reaction (PCR). Ideally, PCR produces an identical copy of a molecule at each cycle. However, PCR can have disadvantages such that each molecule replicates with a stochastic probability, and this probability varies by PCR cycle and gene sequence, resulting in amplification bias and inaccurate gene expression measurements. Stochastic barcodes with unique molecular labels (also referred to as molecular indexes (MIs)) can be used to count the number of molecules and correct for amplification bias. Stochastic barcoding, such as the Precise™ assay (Cellular Research, Inc. (Palo Alto, Calif.)) and Rhapsody™ assay (Becton, Dickinson and Company (Franklin Lakes, N.J.)), can correct for bias induced by PCR and library preparation steps by using molecular labels (MLs) to label mRNAs during reverse transcription (RT). 
     The Precise™ assay can utilize a non-depleting pool of stochastic barcodes with large number, for example 6561 to 65536, unique molecular label sequences on poly(T) oligonucleotides to hybridize to all poly(A)-mRNAs in a sample during the RT step. A stochastic barcode can comprise a universal PCR priming site. During RT, target gene molecules react randomly with stochastic barcodes. Each target molecule can hybridize to a stochastic barcode resulting to generate stochastically barcoded complementary ribonucleotide acid (cDNA) molecules). After labeling, stochastically barcoded cDNA molecules from microwells of a microwell plate can be pooled into a single tube for PCR amplification and sequencing. Raw sequencing data can be analyzed to produce the number of reads, the number of stochastic barcodes with unique molecular label sequences, and the numbers of mRNA molecules. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 10-17; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 18-20. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more first primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more first primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 10-17; one or more first primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more first primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 18-20; one or more second primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more second primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 1; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 2; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 3; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 4. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 1; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 2; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 3; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 85% identity to SEQ ID NO: 4; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 85% identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of an immunoglobulin heavy chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of an immunoglobulin light chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36, or sequence that exhibits at least about 85% identity to a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. 
     Disclosed herein include methods for labeling nucleic acid targets in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; and extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label. 
     Disclosed herein include methods for determining the numbers of nucleic acid targets in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label; and determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences, second molecular labels with distinct sequences, or a combination thereof, associated with the plurality of extended barcoded nucleic acid molecules, or products thereof. 
     Disclosed herein include methods of determining the numbers of a nucleic acid target in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label; amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules each comprising the first molecular label or the second molecular label; and determining the copy number of the nucleic acid target in the sample based on the number of second molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. 
     Disclosed herein include compositions comprising one or more of the oligonucleotide probes and/or primers disclosed herein. Disclosed herein include kits. In some embodiments, the kit comprises one or more the compositions provided herein (e.g., probes and/or primers and/or primer panels capable of hybridizing to a constant domain of an immune receptor (e.g., TCR, BCR)). Disclosed herein include kits. In some embodiments, the kit comprises: a plurality of oligonucleotide barcodes, wherein each of the plurality of oligonucleotide barcodes comprises a molecular label and a target-binding region, and wherein at least 10 of the plurality of oligonucleotide barcodes comprise different molecular label sequences; a reverse transcriptase; a template switching oligonucleotide comprising the target-binding region, or a portion thereof; and a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity. 
     Definitions 
     Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. See, e.g., Singleton et al., Dictionary of Microbiology and Molecular Biology 2nd ed., J. Wiley &amp; Sons (New York, N.Y. 1994); Sambrook et al., Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Press (Cold Spring Harbor, N.Y. 1989). For purposes of the present disclosure, the following terms are defined below. 
     As used herein, the term “adaptor” can mean a sequence to facilitate amplification or sequencing of associated nucleic acids. The associated nucleic acids can comprise target nucleic acids. The associated nucleic acids can comprise one or more of spatial labels, target labels, sample labels, indexing label, or barcode sequences (e.g., molecular labels). The adaptors can be linear. The adaptors can be pre-adenylated adaptors. The adaptors can be double- or single-stranded. One or more adaptor can be located on the 5′ or 3′ end of a nucleic acid. When the adaptors comprise known sequences on the 5′ and 3′ ends, the known sequences can be the same or different sequences. An adaptor located on the 5′ and/or 3′ ends of a polynucleotide can be capable of hybridizing to one or more oligonucleotides immobilized on a surface. An adaptor can, in some embodiments, comprise a universal sequence. A universal sequence can be a region of nucleotide sequence that is common to two or more nucleic acid molecules. The two or more nucleic acid molecules can also have regions of different sequence. Thus, for example, the 5′ adaptors can comprise identical and/or universal nucleic acid sequences and the 3′ adaptors can comprise identical and/or universal sequences. A universal sequence that may be present in different members of a plurality of nucleic acid molecules can allow the replication or amplification of multiple different sequences using a single universal primer that is complementary to the universal sequence. Similarly, at least one, two (e.g., a pair) or more universal sequences that may be present in different members of a collection of nucleic acid molecules can allow the replication or amplification of multiple different sequences using at least one, two (e.g., a pair) or more single universal primers that are complementary to the universal sequences. Thus, a universal primer includes a sequence that can hybridize to such a universal sequence. The target nucleic acid sequence-bearing molecules may be modified to attach universal adaptors (e.g., non-target nucleic acid sequences) to one or both ends of the different target nucleic acid sequences. The one or more universal primers attached to the target nucleic acid can provide sites for hybridization of universal primers. The one or more universal primers attached to the target nucleic acid can be the same or different from each other. 
     As used herein the term “associated” or “associated with” can mean that two or more species are identifiable as being co-located at a point in time. An association can mean that two or more species are or were within a similar container. An association can be an informatics association. For example, digital information regarding two or more species can be stored and can be used to determine that one or more of the species were co-located at a point in time. An association can also be a physical association. In some embodiments, two or more associated species are “tethered”, “attached”, or “immobilized” to one another or to a common solid or semisolid surface. An association may refer to covalent or non-covalent means for attaching labels to solid or semi-solid supports such as beads. An association may be a covalent bond between a target and a label. An association can comprise hybridization between two molecules (such as a target molecule and a label). 
     As used herein, the term “complementary” can refer to the capacity for precise pairing between two nucleotides. For example, if a nucleotide at a given position of a nucleic acid is capable of hydrogen bonding with a nucleotide of another nucleic acid, then the two nucleic acids are considered to be complementary to one another at that position. Complementarity between two single-stranded nucleic acid molecules may be “partial,” in which only some of the nucleotides bind, or it may be complete when total complementarity exists between the single-stranded molecules. A first nucleotide sequence can be said to be the “complement” of a second sequence if the first nucleotide sequence is complementary to the second nucleotide sequence. A first nucleotide sequence can be said to be the “reverse complement” of a second sequence, if the first nucleotide sequence is complementary to a sequence that is the reverse (i.e., the order of the nucleotides is reversed) of the second sequence. As used herein, a “complementary” sequence can refer to a “complement” or a “reverse complement” of a sequence. It is understood from the disclosure that if a molecule can hybridize to another molecule it may be complementary, or partially complementary, to the molecule that is hybridizing. 
     As used herein, the term “digital counting” can refer to a method for estimating a number of target molecules in a sample. Digital counting can include the step of determining a number of unique labels that have been associated with targets in a sample. This methodology, which can be stochastic in nature, transforms the problem of counting molecules from one of locating and identifying identical molecules to a series of yes/no digital questions regarding detection of a set of predefined labels. 
     As used herein, the term “label” or “labels” can refer to nucleic acid codes associated with a target within a sample. A label can be, for example, a nucleic acid label. A label can be an entirely or partially amplifiable label. A label can be entirely or partially sequencable label. A label can be a portion of a native nucleic acid that is identifiable as distinct. A label can be a known sequence. A label can comprise a junction of nucleic acid sequences, for example a junction of a native and non-native sequence. As used herein, the term “label” can be used interchangeably with the terms, “index”, “tag,” or “label-tag.” Labels can convey information. For example, in various embodiments, labels can be used to determine an identity of a sample, a source of a sample, an identity of a cell, and/or a target. 
     As used herein, the term “non-depleting reservoirs” can refer to a pool of barcodes (e.g., stochastic barcodes) made up of many different labels. A non-depleting reservoir can comprise large numbers of different barcodes such that when the non-depleting reservoir is associated with a pool of targets each target is likely to be associated with a unique barcode. The uniqueness of each labeled target molecule can be determined by the statistics of random choice and depends on the number of copies of identical target molecules in the collection compared to the diversity of labels. The size of the resulting set of labeled target molecules can be determined by the stochastic nature of the barcoding process, and analysis of the number of barcodes detected then allows calculation of the number of target molecules present in the original collection or sample. When the ratio of the number of copies of a target molecule present to the number of unique barcodes is low, the labeled target molecules are highly unique (i.e., there is a very low probability that more than one target molecule will have been labeled with a given label). 
     As used herein, the term “nucleic acid” refers to a polynucleotide sequence, or fragment thereof. A nucleic acid can comprise nucleotides. A nucleic acid can be exogenous or endogenous to a cell. A nucleic acid can exist in a cell-free environment. A nucleic acid can be a gene or fragment thereof. A nucleic acid can be DNA. A nucleic acid can be RNA. A nucleic acid can comprise one or more analogs (e.g., altered backbone, sugar, or nucleobase). Some non-limiting examples of analogs include: 5-bromouracil, peptide nucleic acid, xeno nucleic acid, morpholinos, locked nucleic acids, glycol nucleic acids, threose nucleic acids, dideoxynucleotides, cordycepin, 7-deaza-GTP, fluorophores (e.g., rhodamine or fluorescein linked to the sugar), thiol containing nucleotides, biotin linked nucleotides, fluorescent base analogs, CpG islands, methyl-7-guanosine, methylated nucleotides, inosine, thiouridine, pseudouridine, dihydrouridine, queuosine, and wyosine. “Nucleic acid”, “polynucleotide, “target polynucleotide”, and “target nucleic acid” can be used interchangeably. 
     A nucleic acid can comprise one or more modifications (e.g., a base modification, a backbone modification), to provide the nucleic acid with a new or enhanced feature (e.g., improved stability). A nucleic acid can comprise a nucleic acid affinity tag. A nucleoside can be a base-sugar combination. The base portion of the nucleoside can be a heterocyclic base. The two most common classes of such heterocyclic bases are the purines and the pyrimidines. Nucleotides can be nucleosides that further include a phosphate group covalently linked to the sugar portion of the nucleoside. For those nucleosides that include a pentofuranosyl sugar, the phosphate group can be linked to the 2′, the 3′, or the 5′ hydroxyl moiety of the sugar. In forming nucleic acids, the phosphate groups can covalently link adjacent nucleosides to one another to form a linear polymeric compound. In turn, the respective ends of this linear polymeric compound can be further joined to form a circular compound; however, linear compounds are generally suitable. In addition, linear compounds may have internal nucleotide base complementarity and may therefore fold in a manner as to produce a fully or partially double-stranded compound. Within nucleic acids, the phosphate groups can commonly be referred to as forming the internucleoside backbone of the nucleic acid. The linkage or backbone can be a 3′ to 5′ phosphodiester linkage. 
     A nucleic acid can comprise a modified backbone and/or modified internucleoside linkages. Modified backbones can include those that retain a phosphorus atom in the backbone and those that do not have a phosphorus atom in the backbone. Suitable modified nucleic acid backbones containing a phosphorus atom therein can include, for example, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkyl phosphotriesters, methyl and other alkyl phosphonate such as 3′-alkylene phosphonates, 5′-alkylene phosphonates, chiral phosphonates, phosphinates, phosphoramidates including 3′-amino phosphoramidate and aminoalkyl phosphoramidates, phosphorodiamidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, selenophosphates, and boranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogs, and those having inverted polarity wherein one or more internucleotide linkages is a 3′ to 3′, a 5′ to 5′ or a 2′ to 2′ linkage. 
     A nucleic acid can comprise polynucleotide backbones that are formed by short chain alkyl or cycloalkyl internucleoside linkages, mixed heteroatom and alkyl or cycloalkyl internucleoside linkages, or one or more short chain heteroatomic or heterocyclic internucleoside linkages. These can include those having morpholino linkages (formed in part from the sugar portion of a nucleoside); siloxane backbones; sulfide, sulfoxide and sulfone backbones; formacetyl and thioformacetyl backbones; methylene formacetyl and thioformacetyl backbones; riboacetyl backbones; alkene containing backbones; sulfamate backbones; methyleneimino and methylenehydrazino backbones; sulfonate and sulfonamide backbones; amide backbones; and others having mixed N, O, S and CH 2  component parts. 
     A nucleic acid can comprise a nucleic acid mimetic. The term “mimetic” can be intended to include polynucleotides wherein only the furanose ring or both the furanose ring and the internucleotide linkage are replaced with non-furanose groups, replacement of only the furanose ring can also be referred as being a sugar surrogate. The heterocyclic base moiety or a modified heterocyclic base moiety can be maintained for hybridization with an appropriate target nucleic acid. One such nucleic acid can be a peptide nucleic acid (PNA). In a PNA, the sugar-backbone of a polynucleotide can be replaced with an amide containing backbone, in particular an aminoethylglycine backbone. The nucleotides can be retained and are bound directly or indirectly to aza nitrogen atoms of the amide portion of the backbone. The backbone in PNA compounds can comprise two or more linked aminoethylglycine units which gives PNA an amide containing backbone. The heterocyclic base moieties can be bound directly or indirectly to aza nitrogen atoms of the amide portion of the backbone. 
     A nucleic acid can comprise a morpholino backbone structure. For example, a nucleic acid can comprise a 6-membered morpholino ring in place of a ribose ring. In some of these embodiments, a phosphorodiamidate or other non-phosphodiester internucleoside linkage can replace a phosphodiester linkage. 
     A nucleic acid can comprise linked morpholino units (e.g., morpholino nucleic acid) having heterocyclic bases attached to the morpholino ring. Linking groups can link the morpholino monomeric units in a morpholino nucleic acid. Non-ionic morpholino-based oligomeric compounds can have less undesired interactions with cellular proteins. Morpholino-based polynucleotides can be nonionic mimics of nucleic acids. A variety of compounds within the morpholino class can be joined using different linking groups. A further class of polynucleotide mimetic can be referred to as cyclohexenyl nucleic acids (CeNA). The furanose ring normally present in a nucleic acid molecule can be replaced with a cyclohexenyl ring. CeNA DMT protected phosphoramidite monomers can be prepared and used for oligomeric compound synthesis using phosphoramidite chemistry. The incorporation of CeNA monomers into a nucleic acid chain can increase the stability of a DNA/RNA hybrid. CeNA oligoadenylates can form complexes with nucleic acid complements with similar stability to the native complexes. A further modification can include Locked Nucleic Acids (LNAs) in which the 2′-hydroxyl group is linked to the 4′ carbon atom of the sugar ring thereby forming a 2′-C, 4′-C-oxymethylene linkage thereby forming a bicyclic sugar moiety. The linkage can be a methylene (—CH 2 ), group bridging the 2′ oxygen atom and the 4′ carbon atom wherein n is 1 or 2. LNA and LNA analogs can display very high duplex thermal stabilities with complementary nucleic acid (Tm=+3 to +10° C.), stability towards 3′-exonucleolytic degradation and good solubility properties. 
     A nucleic acid may also include nucleobase (often referred to simply as “base”) modifications or substitutions. As used herein, “unmodified” or “natural” nucleobases can include the purine bases, (e.g., adenine (A) and guanine (G)), and the pyrimidine bases, (e.g., thymine (T), cytosine (C) and uracil (U)). Modified nucleobases can include other synthetic and natural nucleobases such as 5-methylcytosine (5-me-C), 5-hydroxymethyl cytosine, xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkyl derivatives of adenine and guanine, 2-propyl and other alkyl derivatives of adenine and guanine, 2-thiouracil, 2-thiothymine and 2-thiocytosine, 5-halouracil and cytosine, 5-propynyl (—C═C—CH3) uracil and cytosine and other alkynyl derivatives of pyrimidine bases, 6-azo uracil, cytosine and thymine, 5-uracil (pseudouracil), 4-thiouracil, 8-halo, 8-amino, 8-thiol, 8-thioalkyl, 8-hydroxyl and other 8-substituted adenines and guanines, 5-halo particularly 5-bromo, 5-trifluoromethyl and other 5-substituted uracils and cytosines, 7-methylguanine and 7-methyladenine, 2-F-adenine, 2-aminoadenine, 8-azaguanine and 8-azaadenine, 7-deazaguanine and 7-deazaadenine and 3-deazaguanine and 3-deazaadenine. Modified nucleobases can include tricyclic pyrimidines such as phenoxazine cytidine(1H-pyrimido(5,4-b)(1,4)benzoxazin-2(3H)-one), phenothiazine cytidine (1H-pyrimido(5,4-b)(1,4)benzothiazin-2(3H)-one), G-clamps such as a substituted phenoxazine cytidine (e.g., 9-(2-aminoethoxy)-H-pyrimido(5,4-(b) (1,4)benzoxazin-2(3H)-one), phenothiazine cytidine (1H-pyrimido(5,4-b)(1,4)benzothiazin-2(3H)-one), G-clamps such as a substituted phenoxazine cytidine (e.g., 9-(2-aminoethoxy)-H-pyrimido(5,4-(b) (1,4)benzoxazin-2(3H)-one), carbazole cytidine (2H-pyrimido(4, -b)indol-2-one), pyridoindole cytidine (H-pyrido(3′,2′:4,5)pyrrolo[2,3-d]pyrimidin-2-one). 
     As used herein, the term “sample” can refer to a composition comprising targets. Suitable samples for analysis by the disclosed methods, devices, and systems include cells, tissues, organs, or organisms. 
     As used herein, the term “sampling device” or “device” can refer to a device which may take a section of a sample and/or place the section on a substrate. A sample device can refer to, for example, a fluorescence activated cell sorting (FACS) machine, a cell sorter machine, a biopsy needle, a biopsy device, a tissue sectioning device, a microfluidic device, a blade grid, and/or a microtome. 
     As used herein, the term “solid support” can refer to discrete solid or semi-solid surfaces to which a plurality of barcodes (e.g., stochastic barcodes) may be attached. A solid support may encompass any type of solid, porous, or hollow sphere, ball, bearing, cylinder, or other similar configuration composed of plastic, ceramic, metal, or polymeric material (e.g., hydrogel) onto which a nucleic acid may be immobilized (e.g., covalently or non-covalently). A solid support may comprise a discrete particle that may be spherical (e.g., microspheres) or have a non-spherical or irregular shape, such as cubic, cuboid, pyramidal, cylindrical, conical, oblong, or disc-shaped, and the like. A bead can be non-spherical in shape. A plurality of solid supports spaced in an array may not comprise a substrate. A solid support may be used interchangeably with the term “bead.” 
     As used herein, the term “stochastic barcode” can refer to a polynucleotide sequence comprising labels of the present disclosure. A stochastic barcode can be a polynucleotide sequence that can be used for stochastic barcoding. Stochastic barcodes can be used to quantify targets within a sample. Stochastic barcodes can be used to control for errors which may occur after a label is associated with a target. For example, a stochastic barcode can be used to assess amplification or sequencing errors. A stochastic barcode associated with a target can be called a stochastic barcode-target or stochastic barcode-tag-target. 
     As used herein, the term “gene-specific stochastic barcode” can refer to a polynucleotide sequence comprising labels and a target-binding region that is gene-specific. A stochastic barcode can be a polynucleotide sequence that can be used for stochastic barcoding. Stochastic barcodes can be used to quantify targets within a sample. Stochastic barcodes can be used to control for errors which may occur after a label is associated with a target. For example, a stochastic barcode can be used to assess amplification or sequencing errors. A stochastic barcode associated with a target can be called a stochastic barcode-target or stochastic barcode-tag-target. 
     As used herein, the term “stochastic barcoding” can refer to the random labeling (e.g., barcoding) of nucleic acids. Stochastic barcoding can utilize a recursive Poisson strategy to associate and quantify labels associated with targets. As used herein, the term “stochastic barcoding” can be used interchangeably with “stochastic labeling.” 
     As used here, the term “target” can refer to a composition which can be associated with a barcode (e.g., a stochastic barcode). Exemplary suitable targets for analysis by the disclosed methods, devices, and systems include oligonucleotides, DNA, RNA, mRNA, microRNA, tRNA, and the like. Targets can be single or double stranded. In some embodiments, targets can be proteins, peptides, or polypeptides. In some embodiments, targets are lipids. As used herein, “target” can be used interchangeably with “species.” 
     As used herein, the term “reverse transcriptases” can refer to a group of enzymes having reverse transcriptase activity (i.e., that catalyze synthesis of DNA from an RNA template). In general, such enzymes include, but are not limited to, retroviral reverse transcriptase, retrotransposon reverse transcriptase, retroplasmid reverse transcriptases, retron reverse transcriptases, bacterial reverse transcriptases, group II intron-derived reverse transcriptase, and mutants, variants or derivatives thereof. Non-retroviral reverse transcriptases include non-LTR retrotransposon reverse transcriptases, retroplasmid reverse transcriptases, retron reverse transcriptases, and group II intron reverse transcriptases. Examples of group II intron reverse transcriptases include the  Lactococcus lactis  LI.LtrB intron reverse transcriptase, the  Thermosynechococcus  elongatus TeI4c intron reverse transcriptase, or the  Geobacillus stearothermophilus  GsI-IIC intron reverse transcriptase. Other classes of reverse transcriptases can include many classes of non-retroviral reverse transcriptases (i.e., retrons, group II introns, and diversity-generating retroelements among others). 
     The terms “universal adaptor primer,” “universal primer adaptor” or “universal adaptor sequence” are used interchangeably to refer to a nucleotide sequence that can be used to hybridize to barcodes (e.g., stochastic barcodes) to generate gene-specific barcodes. A universal adaptor sequence can, for example, be a known sequence that is universal across all barcodes used in methods of the disclosure. For example, when multiple targets are being labeled using the methods disclosed herein, each of the target-specific sequences may be linked to the same universal adaptor sequence. In some embodiments, more than one universal adaptor sequences may be used in the methods disclosed herein. For example, when multiple targets are being labeled using the methods disclosed herein, at least two of the target-specific sequences are linked to different universal adaptor sequences. A universal adaptor primer and its complement may be included in two oligonucleotides, one of which comprises a target-specific sequence and the other comprises a barcode. For example, a universal adaptor sequence may be part of an oligonucleotide comprising a target-specific sequence to generate a nucleotide sequence that is complementary to a target nucleic acid. A second oligonucleotide comprising a barcode and a complementary sequence of the universal adaptor sequence may hybridize with the nucleotide sequence and generate a target-specific barcode (e.g., a target-specific stochastic barcode). In some embodiments, a universal adaptor primer has a sequence that is different from a universal PCR primer used in the methods of this disclosure. 
     Barcodes 
     Barcoding, such as stochastic barcoding, has been described in, for example, US 2015/0299784, WO 2015/031691, and Fu et al, Proc Natl Acad Sci U.S.A. 2011 May 31; 108(22):9026-31, the content of these publications is incorporated hereby in its entirety. In some embodiments, the barcode disclosed herein can be a stochastic barcode which can be a polynucleotide sequence that may be used to stochastically label (e.g., barcode, tag) a target. Barcodes can be referred to stochastic barcodes if the ratio of the number of different barcode sequences of the stochastic barcodes and the number of occurrence of any of the targets to be labeled can be, or be about, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, or a number or a range between any two of these values. A target can be an mRNA species comprising mRNA molecules with identical or nearly identical sequences. Barcodes can be referred to as stochastic barcodes if the ratio of the number of different barcode sequences of the stochastic barcodes and the number of occurrence of any of the targets to be labeled is at least, or is at most, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, or 100:1. Barcode sequences of stochastic barcodes can be referred to as molecular labels. 
     A barcode, for example a stochastic barcode, can comprise one or more labels. Exemplary labels can include a universal label, a cell label, a barcode sequence (e.g., a molecular label), a sample label, a plate label, a spatial label, and/or a pre-spatial label.  FIG.  1    illustrates an exemplary barcode  104  with a spatial label. The barcode  104  can comprise a 5′amine that may link the barcode to a solid support  105 . The barcode can comprise a universal label, a dimension label, a spatial label, a cell label, and/or a molecular label. The order of different labels (including but not limited to the universal label, the dimension label, the spatial label, the cell label, and the molecule label) in the barcode can vary. For example, as shown in  FIG.  1   , the universal label may be the 5′-most label, and the molecular label may be the 3′-most label. The spatial label, dimension label, and the cell label may be in any order. In some embodiments, the universal label, the spatial label, the dimension label, the cell label, and the molecular label are in any order. The barcode can comprise a target-binding region. The target-binding region can interact with a target (e.g., target nucleic acid, RNA, mRNA, DNA) in a sample. For example, a target-binding region can comprise an oligo(dT) sequence which can interact with poly(A) tails of mRNAs. In some instances, the labels of the barcode (e.g., universal label, dimension label, spatial label, cell label, and barcode sequence) may be separated by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 or more nucleotides. 
     A label, for example the cell label, can comprise a unique set of nucleic acid sub-sequences of defined length, e.g., seven nucleotides each (equivalent to the number of bits used in some Hamming error correction codes), which can be designed to provide error correction capability. The set of error correction sub-sequences comprise seven nucleotide sequences can be designed such that any pairwise combination of sequences in the set exhibits a defined “genetic distance” (or number of mismatched bases), for example, a set of error correction sub-sequences can be designed to exhibit a genetic distance of three nucleotides. In this case, review of the error correction sequences in the set of sequence data for labeled target nucleic acid molecules (described more fully below) can allow one to detect or correct amplification or sequencing errors. In some embodiments, the length of the nucleic acid sub-sequences used for creating error correction codes can vary, for example, they can be, or be about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 31, 40, 50, or a number or a range between any two of these values, nucleotides in length. In some embodiments, nucleic acid sub-sequences of other lengths can be used for creating error correction codes. 
     The barcode can comprise a target-binding region. The target-binding region can interact with a target in a sample. The target can be, or comprise, ribonucleic acids (RNAs), messenger RNAs (mRNAs), microRNAs, small interfering RNAs (siRNAs), RNA degradation products, RNAs each comprising a poly(A) tail, or any combination thereof. In some embodiments, the plurality of targets can include deoxyribonucleic acids (DNAs). 
     In some embodiments, a target-binding region can comprise an oligo(dT) sequence which can interact with poly(A) tails of mRNAs. One or more of the labels of the barcode (e.g., the universal label, the dimension label, the spatial label, the cell label, and the barcode sequences (e.g., molecular label)) can be separated by a spacer from another one or two of the remaining labels of the barcode. The spacer can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, or more nucleotides. In some embodiments, none of the labels of the barcode is separated by spacer. 
     Universal Labels 
     A barcode can comprise one or more universal labels. In some embodiments, the one or more universal labels can be the same for all barcodes in the set of barcodes attached to a given solid support. In some embodiments, the one or more universal labels can be the same for all barcodes attached to a plurality of beads. In some embodiments, a universal label can comprise a nucleic acid sequence that is capable of hybridizing to a sequencing primer. Sequencing primers can be used for sequencing barcodes comprising a universal label. Sequencing primers (e.g., universal sequencing primers) can comprise sequencing primers associated with high-throughput sequencing platforms. In some embodiments, a universal label can comprise a nucleic acid sequence that is capable of hybridizing to a PCR primer. In some embodiments, the universal label can comprise a nucleic acid sequence that is capable of hybridizing to a sequencing primer and a PCR primer. The nucleic acid sequence of the universal label that is capable of hybridizing to a sequencing or PCR primer can be referred to as a primer binding site. A universal label can comprise a sequence that can be used to initiate transcription of the barcode. A universal label can comprise a sequence that can be used for extension of the barcode or a region within the barcode. A universal label can be, or be about, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a number or a range between any two of these values, nucleotides in length. For example, a universal label can comprise at least about 10 nucleotides. A universal label can be at least, or be at most, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, or 300 nucleotides in length. In some embodiments, a cleavable linker or modified nucleotide can be part of the universal label sequence to enable the barcode to be cleaved off from the support. 
     Dimension Labels 
     A barcode can comprise one or more dimension labels. In some embodiments, a dimension label can comprise a nucleic acid sequence that provides information about a dimension in which the labeling (e.g., stochastic labeling) occurred. For example, a dimension label can provide information about the time at which a target was barcoded. A dimension label can be associated with a time of barcoding (e.g., stochastic barcoding) in a sample. A dimension label can be activated at the time of labeling. Different dimension labels can be activated at different times. The dimension label provides information about the order in which targets, groups of targets, and/or samples were barcoded. For example, a population of cells can be barcoded at the G0 phase of the cell cycle. The cells can be pulsed again with barcodes (e.g., stochastic barcodes) at the G1 phase of the cell cycle. The cells can be pulsed again with barcodes at the S phase of the cell cycle, and so on. Barcodes at each pulse (e.g., each phase of the cell cycle), can comprise different dimension labels. In this way, the dimension label provides information about which targets were labelled at which phase of the cell cycle. Dimension labels can interrogate many different biological times. Exemplary biological times can include, but are not limited to, the cell cycle, transcription (e.g., transcription initiation), and transcript degradation. In another example, a sample (e.g., a cell, a population of cells) can be labeled before and/or after treatment with a drug and/or therapy. The changes in the number of copies of distinct targets can be indicative of the sample&#39;s response to the drug and/or therapy. 
     A dimension label can be activatable. An activatable dimension label can be activated at a specific time point. The activatable label can be, for example, constitutively activated (e.g., not turned off). The activatable dimension label can be, for example, reversibly activated (e.g., the activatable dimension label can be turned on and turned off). The dimension label can be, for example, reversibly activatable at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times. The dimension label can be reversibly activatable, for example, at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more times. In some embodiments, the dimension label can be activated with fluorescence, light, a chemical event (e.g., cleavage, ligation of another molecule, addition of modifications (e.g., pegylated, sumoylated, acetylated, methylated, deacetylated, demethylated), a photochemical event (e.g., photocaging), and introduction of a non-natural nucleotide. 
     The dimension label can, in some embodiments, be identical for all barcodes (e.g., stochastic barcodes) attached to a given solid support (e.g., a bead), but different for different solid supports (e.g., beads). In some embodiments, at least 60%, 70%, 80%, 85%, 90%, 95%, 97%, 99% or 100%, of barcodes on the same solid support can comprise the same dimension label. In some embodiments, at least 60% of barcodes on the same solid support can comprise the same dimension label. In some embodiments, at least 95% of barcodes on the same solid support can comprise the same dimension label. 
     There can be as many as 10 6  or more unique dimension label sequences represented in a plurality of solid supports (e.g., beads). A dimension label can be, or be about 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a number or a range between any two of these values, nucleotides in length. A dimension label can be at least, or be at most, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, or 300, nucleotides in length. A dimension label can comprise between about 5 to about 200 nucleotides. A dimension label can comprise between about 10 to about 150 nucleotides. A dimension label can comprise between about 20 to about 125 nucleotides in length. 
     Spatial Labels 
     A barcode can comprise one or more spatial labels. In some embodiments, a spatial label can comprise a nucleic acid sequence that provides information about the spatial orientation of a target molecule which is associated with the barcode. A spatial label can be associated with a coordinate in a sample. The coordinate can be a fixed coordinate. For example, a coordinate can be fixed in reference to a substrate. A spatial label can be in reference to a two or three-dimensional grid. A coordinate can be fixed in reference to a landmark. The landmark can be identifiable in space. A landmark can be a structure which can be imaged. A landmark can be a biological structure, for example an anatomical landmark. A landmark can be a cellular landmark, for instance an organelle. A landmark can be a non-natural landmark such as a structure with an identifiable identifier such as a color code, bar code, magnetic property, fluorescents, radioactivity, or a unique size or shape. A spatial label can be associated with a physical partition (e.g., a well, a container, or a droplet). In some embodiments, multiple spatial labels are used together to encode one or more positions in space. 
     The spatial label can be identical for all barcodes attached to a given solid support (e.g., a bead), but different for different solid supports (e.g., beads). In some embodiments, the percentage of barcodes on the same solid support comprising the same spatial label can be, or be about, 60%, 70%, 80%, 85%, 90%, 95%, 97%, 99%, 100%, or a number or a range between any two of these values. In some embodiments, the percentage of barcodes on the same solid support comprising the same spatial label can be at least, or be at most, 60%, 70%, 80%, 85%, 90%, 95%, 97%, 99%, or 100%. In some embodiments, at least 60% of barcodes on the same solid support can comprise the same spatial label. In some embodiments, at least 95% of barcodes on the same solid support can comprise the same spatial label. 
     There can be as many as 10 6  or more unique spatial label sequences represented in a plurality of solid supports (e.g., beads). A spatial label can be, or be about, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a number or a range between any two of these values, nucleotides in length. A spatial label can be at least or at most 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, or 300 nucleotides in length. A spatial label can comprise between about 5 to about 200 nucleotides. A spatial label can comprise between about 10 to about 150 nucleotides. A spatial label can comprise between about 20 to about 125 nucleotides in length. 
     Cell Labels 
     A barcode (e.g., a stochastic barcode) can comprise one or more cell labels. In some embodiments, a cell label can comprise a nucleic acid sequence that provides information for determining which target nucleic acid originated from which cell. In some embodiments, the cell label is identical for all barcodes attached to a given solid support (e.g., a bead), but different for different solid supports (e.g., beads). In some embodiments, the percentage of barcodes on the same solid support comprising the same cell label can be, or be about 60%, 70%, 80%, 85%, 90%, 95%, 97%, 99%, 100%, or a number or a range between any two of these values. In some embodiments, the percentage of barcodes on the same solid support comprising the same cell label can be, or be about 60%, 70%, 80%, 85%, 90%, 95%, 97%, 99%, or 100%. For example, at least 60% of barcodes on the same solid support can comprise the same cell label. As another example, at least 95% of barcodes on the same solid support can comprise the same cell label. 
     There can be as many as 10 6  or more unique cell label sequences represented in a plurality of solid supports (e.g., beads). A cell label can be, or be about, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a number or a range between any two of these values, nucleotides in length. A cell label can be at least, or be at most, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, or 300 nucleotides in length. For example, a cell label can comprise between about 5 to about 200 nucleotides. As another example, a cell label can comprise between about 10 to about 150 nucleotides. As yet another example, a cell label can comprise between about 20 to about 125 nucleotides in length. 
     Barcode Sequences 
     A barcode can comprise one or more barcode sequences. In some embodiments, a barcode sequence can comprise a nucleic acid sequence that provides identifying information for the specific type of target nucleic acid species hybridized to the barcode. A barcode sequence can comprise a nucleic acid sequence that provides a counter (e.g., that provides a rough approximation) for the specific occurrence of the target nucleic acid species hybridized to the barcode (e.g., target-binding region). 
     In some embodiments, a diverse set of barcode sequences are attached to a given solid support (e.g., a bead). In some embodiments, there can be, or be about, 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , or a number or a range between any two of these values, unique molecular label sequences. For example, a plurality of barcodes can comprise about 6561 barcodes sequences with distinct sequences. As another example, a plurality of barcodes can comprise about 65536 barcode sequences with distinct sequences. In some embodiments, there can be at least, or be at most, 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , or 10 9 , unique barcode sequences. The unique molecular label sequences can be attached to a given solid support (e.g., a bead). In some embodiments, the unique molecular label sequence is partially or entirely encompassed by a particle (e.g., a hydrogel bead). 
     The length of a barcode can be different in different implementations. For example, a barcode can be, or be about, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a number or a range between any two of these values, nucleotides in length. As another example, a barcode can be at least, or be at most, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, or 300 nucleotides in length. 
     Molecular Labels 
     A barcode (e.g., a stochastic barcode) can comprise one or more molecular labels. Molecular labels can include barcode sequences. In some embodiments, a molecular label can comprise a nucleic acid sequence that provides identifying information for the specific type of target nucleic acid species hybridized to the barcode. A molecular label can comprise a nucleic acid sequence that provides a counter for the specific occurrence of the target nucleic acid species hybridized to the barcode (e.g., target-binding region). 
     In some embodiments, a diverse set of molecular labels are attached to a given solid support (e.g., a bead). In some embodiments, there can be, or be about, 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , or a number or a range between any two of these values, of unique molecular label sequences. For example, a plurality of barcodes can comprise about 6561 molecular labels with distinct sequences. As another example, a plurality of barcodes can comprise about 65536 molecular labels with distinct sequences. In some embodiments, there can be at least, or be at most, 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , or 10 9 , unique molecular label sequences. Barcodes with unique molecular label sequences can be attached to a given solid support (e.g., a bead). 
     For barcoding (e.g., stochastic barcoding) using a plurality of stochastic barcodes, the ratio of the number of different molecular label sequences and the number of occurrence of any of the targets can be, or be about, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, or a number or a range between any two of these values. A target can be an mRNA species comprising mRNA molecules with identical or nearly identical sequences. In some embodiments, the ratio of the number of different molecular label sequences and the number of occurrence of any of the targets is at least, or is at most, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, or 100:1. 
     A molecular label can be, or be about, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a number or a range between any two of these values, nucleotides in length. A molecular label can be at least, or be at most, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, or 300 nucleotides in length. 
     Target-Binding Region 
     A barcode can comprise one or more target binding regions, such as capture probes. In some embodiments, a target-binding region can hybridize with a target of interest. In some embodiments, the target binding regions can comprise a nucleic acid sequence that hybridizes specifically to a target (e.g., target nucleic acid, target molecule, e.g., a cellular nucleic acid to be analyzed), for example to a specific gene sequence. In some embodiments, a target binding region can comprise a nucleic acid sequence that can attach (e.g., hybridize) to a specific location of a specific target nucleic acid. In some embodiments, the target binding region can comprise a nucleic acid sequence that is capable of specific hybridization to a restriction enzyme site overhang (e.g., an EcoRI sticky-end overhang). The barcode can then ligate to any nucleic acid molecule comprising a sequence complementary to the restriction site overhang. 
     In some embodiments, a target binding region can comprise a non-specific target nucleic acid sequence. A non-specific target nucleic acid sequence can refer to a sequence that can bind to multiple target nucleic acids, independent of the specific sequence of the target nucleic acid. For example, target binding region can comprise a random multimer sequence, or an oligo(dT) sequence that hybridizes to the poly(A) tail on mRNA molecules. A random multimer sequence can be, for example, a random dimer, trimer, quatramer, pentamer, hexamer, septamer, octamer, nonamer, decamer, or higher multimer sequence of any length. In some embodiments, the target binding region is the same for all barcodes attached to a given bead. In some embodiments, the target binding regions for the plurality of barcodes attached to a given bead can comprise two or more different target binding sequences. A target binding region can be, or be about, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a number or a range between any two of these values, nucleotides in length. A target binding region can be at most about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or more nucleotides in length. 
     In some embodiments, a target-binding region can comprise an oligo(dT) which can hybridize with mRNAs comprising polyadenylated ends. A target-binding region can be gene-specific. For example, a target-binding region can be configured to hybridize to a specific region of a target. A target-binding region can be, or be about, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 27, 28, 29, 30, or a number or a range between any two of these values, nucleotides in length. A target-binding region can be at least, or be at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 27, 28, 29, or 30, nucleotides in length. A target-binding region can be about 5-30 nucleotides in length. When a barcode comprises a gene-specific target-binding region, the barcode can be referred to herein as a gene-specific barcode. 
     Orientation Property 
     A stochastic barcode (e.g., a stochastic barcode) can comprise one or more orientation properties which can be used to orient (e.g., align) the barcodes. A barcode can comprise a moiety for isoelectric focusing. Different barcodes can comprise different isoelectric focusing points. When these barcodes are introduced to a sample, the sample can undergo isoelectric focusing in order to orient the barcodes into a known way. In this way, the orientation property can be used to develop a known map of barcodes in a sample. Exemplary orientation properties can include, electrophoretic mobility (e.g., based on size of the barcode), isoelectric point, spin, conductivity, and/or self-assembly. For example, barcodes with an orientation property of self-assembly, can self-assemble into a specific orientation (e.g., nucleic acid nanostructure) upon activation. 
     Affinity Property 
     A barcode (e.g., a stochastic barcode) can comprise one or more affinity properties. For example, a spatial label can comprise an affinity property. An affinity property can include a chemical and/or biological moiety that can facilitate binding of the barcode to another entity (e.g., cell receptor). For example, an affinity property can comprise an antibody, for example, an antibody specific for a specific moiety (e.g., receptor) on a sample. In some embodiments, the antibody can guide the barcode to a specific cell type or molecule. Targets at and/or near the specific cell type or molecule can be labeled (e.g., stochastically labeled). The affinity property can, in some embodiments, provide spatial information in addition to the nucleotide sequence of the spatial label because the antibody can guide the barcode to a specific location. The antibody can be a therapeutic antibody, for example a monoclonal antibody or a polyclonal antibody. The antibody can be humanized or chimeric. The antibody can be a naked antibody or a fusion antibody. 
     The antibody can be a full-length (i.e., naturally occurring or formed by normal immunoglobulin gene fragment recombinatorial processes) immunoglobulin molecule (e.g., an IgG antibody) or an immunologically active (i.e., specifically binding) portion of an immunoglobulin molecule, like an antibody fragment. 
     The antibody fragment can be, for example, a portion of an antibody such as F(ab′)2, Fab′, Fab, Fv, sFv and the like. In some embodiments, the antibody fragment can bind with the same antigen that is recognized by the full-length antibody. The antibody fragment can include isolated fragments consisting of the variable regions of antibodies, such as the “Fv” fragments consisting of the variable regions of the heavy and light chains and recombinant single chain polypeptide molecules in which light and heavy variable regions are connected by a peptide linker (“scFv proteins”). Exemplary antibodies can include, but are not limited to, antibodies for cancer cells, antibodies for viruses, antibodies that bind to cell surface receptors (CD8, CD34, CD45), and therapeutic antibodies. 
     Universal Adaptor Primer 
     A barcode can comprise one or more universal adaptor primers. For example, a gene-specific barcode, such as a gene-specific stochastic barcode, can comprise a universal adaptor primer. A universal adaptor primer can refer to a nucleotide sequence that is universal across all barcodes. A universal adaptor primer can be used for building gene-specific barcodes. A universal adaptor primer can be, or be about, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 27, 28, 29, 30, or a number or a range between any two of these nucleotides in length. A universal adaptor primer can be at least, or be at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 27, 28, 29, or 30 nucleotides in length. A universal adaptor primer can be from 5-30 nucleotides in length. 
     Linker 
     When a barcode comprises more than one of a type of label (e.g., more than one cell label or more than one barcode sequence, such as one molecular label), the labels may be interspersed with a linker label sequence. A linker label sequence can be at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or more nucleotides in length. A linker label sequence can be at most about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or more nucleotides in length. In some instances, a linker label sequence is 12 nucleotides in length. A linker label sequence can be used to facilitate the synthesis of the barcode. The linker label can comprise an error-correcting (e.g., Hamming) code. 
     Solid Supports 
     Barcodes, such as stochastic barcodes, disclosed herein can, in some embodiments, be associated with a solid support. The solid support can be, for example, a synthetic particle. In some embodiments, some or all of the barcode sequences, such as molecular labels for stochastic barcodes (e.g., the first barcode sequences) of a plurality of barcodes (e.g., the first plurality of barcodes) on a solid support differ by at least one nucleotide. The cell labels of the barcodes on the same solid support can be the same. The cell labels of the barcodes on different solid supports can differ by at least one nucleotide. For example, first cell labels of a first plurality of barcodes on a first solid support can have the same sequence, and second cell labels of a second plurality of barcodes on a second solid support can have the same sequence. The first cell labels of the first plurality of barcodes on the first solid support and the second cell labels of the second plurality of barcodes on the second solid support can differ by at least one nucleotide. A cell label can be, for example, about 5-20 nucleotides long. A barcode sequence can be, for example, about 5-20 nucleotides long. The synthetic particle can be, for example, a bead. 
     The bead can be, for example, a silica gel bead, a controlled pore glass bead, a magnetic bead, a Dynabead, a sephadex/sepharose bead, a cellulose bead, a polystyrene bead, or any combination thereof. The bead can comprise a material such as polydimethylsiloxane (PDMS), polystyrene, glass, polypropylene, agarose, gelatin, hydrogel, paramagnetic, ceramic, plastic, glass, methylstyrene, acrylic polymer, titanium, latex, sepharose, cellulose, nylon, silicone, or any combination thereof. 
     In some embodiments, the bead can be a polymeric bead, for example a deformable bead or a gel bead, functionalized with barcodes or stochastic barcodes (such as gel beads from 10X Genomics (San Francisco, Calif.). In some implementation, a gel bead can comprise a polymer-based gels. Gel beads can be generated, for example, by encapsulating one or more polymeric precursors into droplets. Upon exposure of the polymeric precursors to an accelerator (e.g., tetramethylethylenediamine (TEMED)), a gel bead may be generated. 
     In some embodiments, the particle can be disruptable (e.g., dissolvable, degradable). For example, the polymeric bead can dissolve, melt, or degrade, for example, under a desired condition. The desired condition can include an environmental condition. The desired condition may result in the polymeric bead dissolving, melting, or degrading in a controlled manner. A gel bead may dissolve, melt, or degrade due to a chemical stimulus, a physical stimulus, a biological stimulus, a thermal stimulus, a magnetic stimulus, an electric stimulus, a light stimulus, or any combination thereof. 
     Analytes and/or reagents, such as oligonucleotide barcodes, for example, may be coupled/immobilized to the interior surface of a gel bead (e.g., the interior accessible via diffusion of an oligonucleotide barcode and/or materials used to generate an oligonucleotide barcode) and/or the outer surface of a gel bead or any other microcapsule described herein. Coupling/immobilization may be via any form of chemical bonding (e.g., covalent bond, ionic bond) or physical phenomena (e.g., Van der Waals forces, dipole-dipole interactions, etc.). In some embodiments, coupling/immobilization of a reagent to a gel bead or any other microcapsule described herein may be reversible, such as, for example, via a labile moiety (e.g., via a chemical cross-linker, including chemical cross-linkers described herein). Upon application of a stimulus, the labile moiety may be cleaved and the immobilized reagent set free. In some embodiments, the labile moiety is a disulfide bond. For example, in the case where an oligonucleotide barcode is immobilized to a gel bead via a disulfide bond, exposure of the disulfide bond to a reducing agent can cleave the disulfide bond and free the oligonucleotide barcode from the bead. The labile moiety may be included as part of a gel bead or microcapsule, as part of a chemical linker that links a reagent or analyte to a gel bead or microcapsule, and/or as part of a reagent or analyte. In some embodiments, at least one barcode of the plurality of barcodes can be immobilized on the particle, partially immobilized on the particle, enclosed in the particle, partially enclosed in the particle, or any combination thereof. 
     In some embodiments, a gel bead can comprise a wide range of different polymers including but not limited to: polymers, heat sensitive polymers, photosensitive polymers, magnetic polymers, pH sensitive polymers, salt-sensitive polymers, chemically sensitive polymers, polyelectrolytes, polysaccharides, peptides, proteins, and/or plastics. Polymers may include but are not limited to materials such as poly(N-isopropylacrylamide) (PNIPAAm), poly(styrene sulfonate) (PSS), poly(allyl amine) (PAAm), poly(acrylic acid) (PAA), poly(ethylene imine) (PEI), poly(diallyldimethyl-ammonium chloride) (PDADMAC), poly(pyrolle) (PPy), poly(vinylpyrrolidone) (PVPON), poly(vinyl pyridine) (PVP), poly(methacrylic acid) (PMAA), poly(methyl methacrylate) (PMMA), polystyrene (PS), poly(tetrahydrofuran) (PTHF), poly(phthaladehyde) (PTHF), poly(hexyl viologen) (PHV), poly(L-lysine) (PLL), poly(L-arginine) (PARG), poly(lactic-co-glycolic acid) (PLGA). 
     Numerous chemical stimuli can be used to trigger the disruption, dissolution, or degradation of the beads. Examples of these chemical changes may include, but are not limited to pH-mediated changes to the bead wall, disintegration of the bead wall via chemical cleavage of crosslink bonds, triggered depolymerization of the bead wall, and bead wall switching reactions. Bulk changes may also be used to trigger disruption of the beads. 
     Bulk or physical changes to the microcapsule through various stimuli also offer many advantages in designing capsules to release reagents. Bulk or physical changes occur on a macroscopic scale, in which bead rupture is the result of mechano-physical forces induced by a stimulus. These processes may include, but are not limited to pressure induced rupture, bead wall melting, or changes in the porosity of the bead wall. 
     Biological stimuli may also be used to trigger disruption, dissolution, or degradation of beads. Generally, biological triggers resemble chemical triggers, but many examples use biomolecules, or molecules commonly found in living systems such as enzymes, peptides, saccharides, fatty acids, nucleic acids and the like. For example, beads may comprise polymers with peptide cross-links that are sensitive to cleavage by specific proteases. More specifically, one example may comprise a microcapsule comprising GFLGK peptide cross links. Upon addition of a biological trigger such as the protease Cathepsin B, the peptide cross links of the shell well are cleaved and the contents of the beads are released. In other cases, the proteases may be heat-activated. In another example, beads comprise a shell wall comprising cellulose. Addition of the hydrolytic enzyme chitosan serves as biologic trigger for cleavage of cellulosic bonds, depolymerization of the shell wall, and release of its inner contents. 
     The beads may also be induced to release their contents upon the application of a thermal stimulus. A change in temperature can cause a variety changes to the beads. A change in heat may cause melting of a bead such that the bead wall disintegrates. In other cases, the heat may increase the internal pressure of the inner components of the bead such that the bead ruptures or explodes. In still other cases, the heat may transform the bead into a shrunken dehydrated state. The heat may also act upon heat-sensitive polymers within the wall of a bead to cause disruption of the bead. 
     Inclusion of magnetic nanoparticles to the bead wall of microcapsules may allow triggered rupture of the beads as well as guide the beads in an array. A device of this disclosure may comprise magnetic beads for either purpose. In one example, incorporation of Fe 3 O 4  nanoparticles into polyelectrolyte containing beads triggers rupture in the presence of an oscillating magnetic field stimulus. 
     A bead may also be disrupted, dissolved, or degraded as the result of electrical stimulation. Similar to magnetic particles described in the previous section, electrically sensitive beads can allow for both triggered rupture of the beads as well as other functions such as alignment in an electric field, electrical conductivity or redox reactions. In one example, beads containing electrically sensitive material are aligned in an electric field such that release of inner reagents can be controlled. In other examples, electrical fields may induce redox reactions within the bead wall itself that may increase porosity. 
     A light stimulus may also be used to disrupt the beads. Numerous light triggers are possible and may include systems that use various molecules such as nanoparticles and chromophores capable of absorbing photons of specific ranges of wavelengths. For example, metal oxide coatings can be used as capsule triggers. UV irradiation of polyelectrolyte capsules coated with SiO 2  may result in disintegration of the bead wall. In yet another example, photo switchable materials such as azobenzene groups may be incorporated in the bead wall. Upon the application of UV or visible light, chemicals such as these undergo a reversible cis-to-trans isomerization upon absorption of photons. In this aspect, incorporation of photon switches result in a bead wall that may disintegrate or become more porous upon the application of a light trigger. 
     For example, in a non-limiting example of barcoding (e.g., stochastic barcoding) illustrated in  FIG.  2   , after introducing cells such as single cells onto a plurality of microwells of a microwell array at block  208 , beads can be introduced onto the plurality of microwells of the microwell array at block  212 . Each microwell can comprise one bead. The beads can comprise a plurality of barcodes. A barcode can comprise a 5′ amine region attached to a bead. The barcode can comprise a universal label, a barcode sequence (e.g., a molecular label), a target-binding region, or any combination thereof. 
     The barcodes disclosed herein can be associated with (e.g., attached to) a solid support (e.g., a bead). The barcodes associated with a solid support can each comprise a barcode sequence selected from a group comprising at least 100 or 1000 barcode sequences with unique sequences. In some embodiments, different barcodes associated with a solid support can comprise barcode with different sequences. In some embodiments, a percentage of barcodes associated with a solid support comprises the same cell label. For example, the percentage can be, or be about 60%, 70%, 80%, 85%, 90%, 95%, 97%, 99%, 100%, or a number or a range between any two of these values. As another example, the percentage can be at least, or be at most 60%, 70%, 80%, 85%, 90%, 95%, 97%, 99%, or 100%. In some embodiments, barcodes associated with a solid support can have the same cell label. The barcodes associated with different solid supports can have different cell labels selected from a group comprising at least 100 or 1000 cell labels with unique sequences. 
     The barcodes disclosed herein can be associated to (e.g., attached to) a solid support (e.g., a bead). In some embodiments, barcoding the plurality of targets in the sample can be performed with a solid support including a plurality of synthetic particles associated with the plurality of barcodes. In some embodiments, the solid support can include a plurality of synthetic particles associated with the plurality of barcodes. The spatial labels of the plurality of barcodes on different solid supports can differ by at least one nucleotide. The solid support can, for example, include the plurality of barcodes in two dimensions or three dimensions. The synthetic particles can be beads. The beads can be silica gel beads, controlled pore glass beads, magnetic beads, Dynabeads, Sephadex/Sepharose beads, cellulose beads, polystyrene beads, or any combination thereof. The solid support can include a polymer, a matrix, a hydrogel, a needle array device, an antibody, or any combination thereof. In some embodiments, the solid supports can be free floating. In some embodiments, the solid supports can be embedded in a semi-solid or solid array. The barcodes may not be associated with solid supports. The barcodes can be individual nucleotides. The barcodes can be associated with a substrate. 
     As used herein, the terms “tethered,” “attached,” and “immobilized,” are used interchangeably, and can refer to covalent or non-covalent means for attaching barcodes to a solid support. Any of a variety of different solid supports can be used as solid supports for attaching pre-synthesized barcodes or for in situ solid-phase synthesis of barcode. 
     In some embodiments, the solid support is a bead. The bead can comprise one or more types of solid, porous, or hollow sphere, ball, bearing, cylinder, or other similar configuration which a nucleic acid can be immobilized (e.g., covalently or non-covalently). The bead can be, for example, composed of plastic, ceramic, metal, polymeric material, or any combination thereof. A bead can be, or comprise, a discrete particle that is spherical (e.g., microspheres) or have a non-spherical or irregular shape, such as cubic, cuboid, pyramidal, cylindrical, conical, oblong, or disc-shaped, and the like. In some embodiments, a bead can be non-spherical in shape. 
     Beads can comprise a variety of materials including, but not limited to, paramagnetic materials (e.g., magnesium, molybdenum, lithium, and tantalum), superparamagnetic materials (e.g., ferrite (Fe 3 O 4 ; magnetite) nanoparticles), ferromagnetic materials (e.g., iron, nickel, cobalt, some alloys thereof, and some rare earth metal compounds), ceramic, plastic, glass, polystyrene, silica, methylstyrene, acrylic polymers, titanium, latex, Sepharose, agarose, hydrogel, polymer, cellulose, nylon, or any combination thereof. 
     In some embodiments, the bead (e.g., the bead to which the labels are attached) is a hydrogel bead. In some embodiments, the bead comprises hydrogel. 
     Some embodiments disclosed herein include one or more particles (for example, beads). Each of the particles can comprise a plurality of oligonucleotides (e.g., barcodes). Each of the plurality of oligonucleotides can comprise a barcode sequence (e.g., a molecular label sequence), a cell label, and a target-binding region (e.g., an oligo(dT) sequence, a gene-specific sequence, a random multimer, or a combination thereof). The cell label sequence of each of the plurality of oligonucleotides can be the same. The cell label sequences of oligonucleotides on different particles can be different such that the oligonucleotides on different particles can be identified. The number of different cell label sequences can be different in different implementations. In some embodiments, the number of cell label sequences can be, or be about 10, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 100000, 10 6 , 10 7 , 10 8 , 10 9 , a number or a range between any two of these values, or more. In some embodiments, the number of cell label sequences can be at least, or be at most 10, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 100000, 10 6 , 10 7 , 10 8 , or 10 9 . In some embodiments, no more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or more of the plurality of the particles include oligonucleotides with the same cell sequence. In some embodiment, the plurality of particles that include oligonucleotides with the same cell sequence can be at most 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or more. In some embodiments, none of the plurality of the particles has the same cell label sequence. 
     The plurality of oligonucleotides on each particle can comprise different barcode sequences (e.g., molecular labels). In some embodiments, the number of barcode sequences can be, or be about 10, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 100000, 10 6 , 10 7 , 10 8 , 10 9 , or a number or a range between any two of these values. In some embodiments, the number of barcode sequences can be at least, or be at most 10, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 100000, 10 6 , 10 7 , 10 8 , or 10 9 . For example, at least 100 of the plurality of oligonucleotides comprise different barcode sequences. As another example, in a single particle, at least 100, 500, 1000, 5000, 10000, 15000, 20000, 50000, a number or a range between any two of these values, or more of the plurality of oligonucleotides comprise different barcode sequences. Some embodiments provide a plurality of the particles comprising barcodes. In some embodiments, the ratio of an occurrence (or a copy or a number) of a target to be labeled and the different barcode sequences can be at least 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, or more. In some embodiments, each of the plurality of oligonucleotides further comprises a sample label, a universal label, or both. The particle can be, for example, a nanoparticle or microparticle. 
     The size of the beads can vary. For example, the diameter of the bead can range from 0.1 micrometer to 50 micrometers. In some embodiments, the diameter of the bead can be, or be about, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, or 50 micrometers, or a number or a range between any two of these values. 
     The diameter of the bead can be related to the diameter of the wells of the substrate. In some embodiments, the diameter of the bead can be, or be about, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or a number or a range between any two of these values, longer or shorter than the diameter of the well. The diameter of the beads can be related to the diameter of a cell (e.g., a single cell entrapped by a well of the substrate). In some embodiments, the diameter of the bead can be at least, or be at most, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% longer or shorter than the diameter of the well. The diameter of the beads can be related to the diameter of a cell (e.g., a single cell entrapped by a well of the substrate). In some embodiments, the diameter of the bead can be, or be about, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 150%, 200%, 250%, 300%, or a number or a range between any two of these values, longer or shorter than the diameter of the cell. In some embodiments, the diameter of the beads can be at least, or be at most, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 150%, 200%, 250%, or 300% longer or shorter than the diameter of the cell. 
     A bead can be attached to and/or embedded in a substrate. A bead can be attached to and/or embedded in a gel, hydrogel, polymer and/or matrix. The spatial position of a bead within a substrate (e.g., gel, matrix, scaffold, or polymer) can be identified using the spatial label present on the barcode on the bead which can serve as a location address. 
     Examples of beads can include, but are not limited to, streptavidin beads, agarose beads, magnetic beads, Dynabeads®, MACS® microbeads, antibody conjugated beads (e.g., anti-immunoglobulin microbeads), protein A conjugated beads, protein G conjugated beads, protein A/G conjugated beads, protein L conjugated beads, oligo(dT) conjugated beads, silica beads, silica-like beads, anti-biotin microbeads, anti-fluorochrome microbeads, and BcMag™ Carboxyl-Terminated Magnetic Beads. 
     A bead can be associated with (e.g., impregnated with) quantum dots or fluorescent dyes to make it fluorescent in one fluorescence optical channel or multiple optical channels. A bead can be associated with iron oxide or chromium oxide to make it paramagnetic or ferromagnetic. Beads can be identifiable. For example, a bead can be imaged using a camera. A bead can have a detectable code associated with the bead. For example, a bead can comprise a barcode. A bead can change size, for example, due to swelling in an organic or inorganic solution. A bead can be hydrophobic. A bead can be hydrophilic. A bead can be biocompatible. 
     A solid support (e.g., a bead) can be visualized. The solid support can comprise a visualizing tag (e.g., fluorescent dye). A solid support (e.g., a bead) can be etched with an identifier (e.g., a number). The identifier can be visualized through imaging the beads. 
     A solid support can comprise an insoluble, semi-soluble, or insoluble material. A solid support can be referred to as “functionalized” when it includes a linker, a scaffold, a building block, or other reactive moiety attached thereto, whereas a solid support may be “nonfunctionalized” when it lacks such a reactive moiety attached thereto. The solid support can be employed free in solution, such as in a microtiter well format; in a flow-through format, such as in a column; or in a dipstick. 
     The solid support can comprise a membrane, paper, plastic, coated surface, flat surface, glass, slide, chip, or any combination thereof. A solid support can take the form of resins, gels, microspheres, or other geometric configurations. A solid support can comprise silica chips, microparticles, nanoparticles, plates, arrays, capillaries, flat supports such as glass fiber filters, glass surfaces, metal surfaces (steel, gold silver, aluminum, silicon and copper), glass supports, plastic supports, silicon supports, chips, filters, membranes, microwell plates, slides, plastic materials including multiwell plates or membranes (e.g., formed of polyethylene, polypropylene, polyamide, polyvinylidenedifluoride), and/or wafers, combs, pins or needles (e.g., arrays of pins suitable for combinatorial synthesis or analysis) or beads in an array of pits or nanoliter wells of flat surfaces such as wafers (e.g., silicon wafers), wafers with pits with or without filter bottoms. 
     The solid support can comprise a polymer matrix (e.g., gel, hydrogel). The polymer matrix may be able to permeate intracellular space (e.g., around organelles). The polymer matrix may able to be pumped throughout the circulatory system. 
     Substrates and Microwell Array 
     As used herein, a substrate can refer to a type of solid support. A substrate can refer to a solid support that can comprise barcodes or stochastic barcodes of the disclosure. A substrate can, for example, comprise a plurality of microwells. For example, a substrate can be a well array comprising two or more microwells. In some embodiments, a microwell can comprise a small reaction chamber of defined volume. In some embodiments, a microwell can entrap one or more cells. In some embodiments, a microwell can entrap only one cell. In some embodiments, a microwell can entrap one or more solid supports. In some embodiments, a microwell can entrap only one solid support. In some embodiments, a microwell entraps a single cell and a single solid support (e.g., a bead). A microwell can comprise barcode reagents of the disclosure. 
     Methods of Barcoding 
     The disclosure provides for methods for estimating the number of distinct targets at distinct locations in a physical sample (e.g., tissue, organ, tumor, cell). The methods can comprise placing barcodes (e.g., stochastic barcodes) in close proximity with the sample, lysing the sample, associating distinct targets with the barcodes, amplifying the targets and/or digitally counting the targets. The method can further comprise analyzing and/or visualizing the information obtained from the spatial labels on the barcodes. In some embodiments, a method comprises visualizing the plurality of targets in the sample. Mapping the plurality of targets onto the map of the sample can include generating a two-dimensional map or a three-dimensional map of the sample. The two-dimensional map and the three-dimensional map can be generated prior to or after barcoding (e.g., stochastically barcoding) the plurality of targets in the sample. Visualizing the plurality of targets in the sample can include mapping the plurality of targets onto a map of the sample. Mapping the plurality of targets onto the map of the sample can include generating a two-dimensional map or a three-dimensional map of the sample. The two-dimensional map and the three-dimensional map can be generated prior to or after barcoding the plurality of targets in the sample. in some embodiments, the two-dimensional map and the three-dimensional map can be generated before or after lysing the sample. Lysing the sample before or after generating the two-dimensional map or the three-dimensional map can include heating the sample, contacting the sample with a detergent, changing the pH of the sample, or any combination thereof. 
     In some embodiments, barcoding the plurality of targets comprises hybridizing a plurality of barcodes with a plurality of targets to create barcoded targets (e.g., stochastically barcoded targets). Barcoding the plurality of targets can comprise generating an indexed library of the barcoded targets. Generating an indexed library of the barcoded targets can be performed with a solid support comprising the plurality of barcodes (e.g., stochastic barcodes). 
     Contacting a Sample and a Barcode 
     The disclosure provides for methods for contacting a sample (e.g., cells) to a substrate of the disclosure. A sample comprising, for example, a cell, organ, or tissue thin section, can be contacted to barcodes (e.g., stochastic barcodes). The cells can be contacted, for example, by gravity flow wherein the cells can settle and create a monolayer. The sample can be a tissue thin section. The thin section can be placed on the substrate. The sample can be one-dimensional (e.g., forms a planar surface). The sample (e.g., cells) can be spread across the substrate, for example, by growing/culturing the cells on the substrate. 
     When barcodes are in close proximity to targets, the targets can hybridize to the barcode. The barcodes can be contacted at a non-depletable ratio such that each distinct target can associate with a distinct barcode of the disclosure. To ensure efficient association between the target and the barcode, the targets can be cross-linked to barcode. 
     Cell Lysis 
     Following the distribution of cells and barcodes, the cells can be lysed to liberate the target molecules. Cell lysis can be accomplished by any of a variety of means, for example, by chemical or biochemical means, by osmotic shock, or by means of thermal lysis, mechanical lysis, or optical lysis. Cells can be lysed by addition of a cell lysis buffer comprising a detergent (e.g., SDS, Li dodecyl sulfate, Triton X-100, Tween-20, or NP-40), an organic solvent (e.g., methanol or acetone), or digestive enzymes (e.g., proteinase K, pepsin, or trypsin), or any combination thereof. To increase the association of a target and a barcode, the rate of the diffusion of the target molecules can be altered by for example, reducing the temperature and/or increasing the viscosity of the lysate. 
     In some embodiments, the sample can be lysed using a filter paper. The filter paper can be soaked with a lysis buffer on top of the filter paper. The filter paper can be applied to the sample with pressure which can facilitate lysis of the sample and hybridization of the targets of the sample to the substrate. 
     In some embodiments, lysis can be performed by mechanical lysis, heat lysis, optical lysis, and/or chemical lysis. Chemical lysis can include the use of digestive enzymes such as proteinase K, pepsin, and trypsin. Lysis can be performed by the addition of a lysis buffer to the substrate. A lysis buffer can comprise Tris HCl. A lysis buffer can comprise at least about 0.01, 0.05, 0.1, 0.5, or 1 M or more Tris HCl. A lysis buffer can comprise at most about 0.01, 0.05, 0.1, 0.5, or 1 M or more Tris HCL. A lysis buffer can comprise about 0.1 M Tris HCl. The pH of the lysis buffer can be at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. The pH of the lysis buffer can be at most about 1, 2, 3, 4, 5, 6, 7, 8, 9,10, or more. In some embodiments, the pH of the lysis buffer is about 7.5. The lysis buffer can comprise a salt (e.g., LiCl). The concentration of salt in the lysis buffer can be at least about 0.1, 0.5, or 1 M or more. The concentration of salt in the lysis buffer can be at most about 0.1, 0.5, or 1 M or more. In some embodiments, the concentration of salt in the lysis buffer is about 0.5M. The lysis buffer can comprise a detergent (e.g., SDS, Li dodecyl sulfate, triton X, tween, NP-40). The concentration of the detergent in the lysis buffer can be at least about 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, or 7%, or more. The concentration of the detergent in the lysis buffer can be at most about 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, or 7%, or more. In some embodiments, the concentration of the detergent in the lysis buffer is about 1% Li dodecyl sulfate. The time used in the method for lysis can be dependent on the amount of detergent used. In some embodiments, the more detergent used, the less time needed for lysis. The lysis buffer can comprise a chelating agent (e.g., EDTA, EGTA). The concentration of a chelating agent in the lysis buffer can be at least about 1, 5, 10, 15, 20, 25, or 30 mM or more. The concentration of a chelating agent in the lysis buffer can be at most about 1, 5, 10, 15, 20, 25, or 30 mM or more. In some embodiments, the concentration of chelating agent in the lysis buffer is about 10 mM. The lysis buffer can comprise a reducing reagent (e.g., beta-mercaptoethanol, DTT). The concentration of the reducing reagent in the lysis buffer can be at least about 1, 5, 10, 15, or 20 mM or more. The concentration of the reducing reagent in the lysis buffer can be at most about 1, 5, 10, 15, or 20 mM or more. In some embodiments, the concentration of reducing reagent in the lysis buffer is about 5 mM. In some embodiments, a lysis buffer can comprise about 0.1M TrisHCl, about pH 7.5, about 0.5M LiCl, about 1% lithium dodecyl sulfate, about 10 mM EDTA, and about 5 mM DTT. 
     Lysis can be performed at a temperature of about 4, 10, 15, 20, 25, or 30° C. Lysis can be performed for about 1, 5, 10, 15, or 20 or more minutes. A lysed cell can comprise at least about 100000, 200000, 300000, 400000, 500000, 600000, or 700000 or more target nucleic acid molecules. A lysed cell can comprise at most about 100000, 200000, 300000, 400000, 500000, 600000, or 700000 or more target nucleic acid molecules. 
     Attachment of Barcodes to Target Nucleic Acid Molecules 
     Following lysis of the cells and release of nucleic acid molecules therefrom, the nucleic acid molecules can randomly associate with the barcodes of the co-localized solid support. Association can comprise hybridization of a barcode&#39;s target recognition region to a complementary portion of the target nucleic acid molecule (e.g., oligo(dT) of the barcode can interact with a poly(A) tail of a target). The assay conditions used for hybridization (e.g., buffer pH, ionic strength, temperature, etc.) can be chosen to promote formation of specific, stable hybrids. In some embodiments, the nucleic acid molecules released from the lysed cells can associate with the plurality of probes on the substrate (e.g., hybridize with the probes on the substrate). When the probes comprise oligo(dT), mRNA molecules can hybridize to the probes and be reverse transcribed. The oligo(dT) portion of the oligonucleotide can act as a primer for first strand synthesis of the cDNA molecule. For example, in a non-limiting example of barcoding illustrated in  FIG.  2   , at block  216 , mRNA molecules can hybridize to barcodes on beads. For example, single-stranded nucleotide fragments can hybridize to the target-binding regions of barcodes. 
     Attachment can further comprise ligation of a barcode&#39;s target recognition region and a portion of the target nucleic acid molecule. For example, the target binding region can comprise a nucleic acid sequence that can be capable of specific hybridization to a restriction site overhang (e.g., an EcoRI sticky-end overhang). The assay procedure can further comprise treating the target nucleic acids with a restriction enzyme (e.g., EcoRI) to create a restriction site overhang. The barcode can then be ligated to any nucleic acid molecule comprising a sequence complementary to the restriction site overhang. A ligase (e.g., T4 DNA ligase) can be used to join the two fragments. 
     For example, in a non-limiting example of barcoding illustrated in  FIG.  2   , at block  220 , the labeled targets from a plurality of cells (or a plurality of samples) (e.g., target-barcode molecules) can be subsequently pooled, for example, into a tube. The labeled targets can be pooled by, for example, retrieving the barcodes and/or the beads to which the target-barcode molecules are attached. 
     The retrieval of solid support-based collections of attached target-barcode molecules can be implemented by use of magnetic beads and an externally-applied magnetic field. Once the target-barcode molecules have been pooled, all further processing can proceed in a single reaction vessel. Further processing can include, for example, reverse transcription reactions, amplification reactions, cleavage reactions, dissociation reactions, and/or nucleic acid extension reactions. Further processing reactions can be performed within the microwells, that is, without first pooling the labeled target nucleic acid molecules from a plurality of cells. 
     Reverse Transcription 
     The disclosure provides for a method to create a target-barcode conjugate using reverse transcription (e.g., at block  224  of  FIG.  2   ). The target-barcode conjugate can comprise the barcode and a complementary sequence of all or a portion of the target nucleic acid (i.e., a barcoded cDNA molecule, such as a stochastically barcoded cDNA molecule). Reverse transcription of the associated RNA molecule can occur by the addition of a reverse transcription primer along with the reverse transcriptase. The reverse transcription primer can be an oligo(dT) primer, a random hexanucleotide primer, or a target-specific oligonucleotide primer. Oligo(dT) primers can be, or can be about, 12-18 nucleotides in length and bind to the endogenous poly(A) tail at the 3′ end of mammalian mRNA. Random hexanucleotide primers can bind to mRNA at a variety of complementary sites. Target-specific oligonucleotide primers typically selectively prime the mRNA of interest. 
     In some embodiments, reverse transcription of the labeled-RNA molecule can occur by the addition of a reverse transcription primer. In some embodiments, the reverse transcription primer is an oligo(dT) primer, random hexanucleotide primer, or a target-specific oligonucleotide primer. Generally, oligo(dT) primers are 12-18 nucleotides in length and bind to the endogenous poly(A) tail at the 3′ end of mammalian mRNA. Random hexanucleotide primers can bind to mRNA at a variety of complementary sites. Target-specific oligonucleotide primers typically selectively prime the mRNA of interest. 
     Reverse transcription can occur repeatedly to produce multiple labeled-cDNA molecules. The methods disclosed herein can comprise conducting at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 reverse transcription reactions. The method can comprise conducting at least about 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 reverse transcription reactions. 
     Amplification 
     One or more nucleic acid amplification reactions (e.g., at block  228  of  FIG.  2   ) can be performed to create multiple copies of the labeled target nucleic acid molecules. Amplification can be performed in a multiplexed manner, wherein multiple target nucleic acid sequences are amplified simultaneously. The amplification reaction can be used to add sequencing adaptors to the nucleic acid molecules. The amplification reactions can comprise amplifying at least a portion of a sample label, if present. The amplification reactions can comprise amplifying at least a portion of the cellular label and/or barcode sequence (e.g., a molecular label). The amplification reactions can comprise amplifying at least a portion of a sample tag, a cell label, a spatial label, a barcode sequence (e.g., a molecular label), a target nucleic acid, or a combination thereof. The amplification reactions can comprise amplifying 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 100%, or a range or a number between any two of these values, of the plurality of nucleic acids. The method can further comprise conducting one or more cDNA synthesis reactions to produce one or more cDNA copies of target-barcode molecules comprising a sample label, a cell label, a spatial label, and/or a barcode sequence (e.g., a molecular label). 
     In some embodiments, amplification can be performed using a polymerase chain reaction (PCR). As used herein, PCR can refer to a reaction for the in vitro amplification of specific DNA sequences by the simultaneous primer extension of complementary strands of DNA. As used herein, PCR can encompass derivative forms of the reaction, including but not limited to, RT-PCR, real-time PCR, nested PCR, quantitative PCR, multiplexed PCR, digital PCR, and assembly PCR. 
     Amplification of the labeled nucleic acids can comprise non-PCR based methods. Examples of non-PCR based methods include, but are not limited to, multiple displacement amplification (MDA), transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), strand displacement amplification (SDA), real-time SDA, rolling circle amplification, or circle-to-circle amplification. Other non-PCR-based amplification methods include multiple cycles of DNA-dependent RNA polymerase-driven RNA transcription amplification or RNA-directed DNA synthesis and transcription to amplify DNA or RNA targets, a ligase chain reaction (LCR), and a Qβ replicase (Qβ) method, use of palindromic probes, strand displacement amplification, oligonucleotide-driven amplification using a restriction endonuclease, an amplification method in which a primer is hybridized to a nucleic acid sequence and the resulting duplex is cleaved prior to the extension reaction and amplification, strand displacement amplification using a nucleic acid polymerase lacking 5′ exonuclease activity, rolling circle amplification, and ramification extension amplification (RAM). In some embodiments, the amplification does not produce circularized transcripts. 
     In some embodiments, the methods disclosed herein further comprise conducting a polymerase chain reaction on the labeled nucleic acid (e.g., labeled-RNA, labeled-DNA, labeled-cDNA) to produce a labeled amplicon (e.g., a stochastically labeled amplicon). The labeled amplicon can be double-stranded molecule. The double-stranded molecule can comprise a double-stranded RNA molecule, a double-stranded DNA molecule, or a RNA molecule hybridized to a DNA molecule. One or both of the strands of the double-stranded molecule can comprise a sample label, a spatial label, a cell label, and/or a barcode sequence (e.g., a molecular label). The labeled amplicon can be a single-stranded molecule. The single-stranded molecule can comprise DNA, RNA, or a combination thereof. The nucleic acids of the disclosure can comprise synthetic or altered nucleic acids. 
     Amplification can comprise use of one or more non-natural nucleotides. Non-natural nucleotides can comprise photolabile or triggerable nucleotides. Examples of non-natural nucleotides can include, but are not limited to, peptide nucleic acid (PNA), morpholino and locked nucleic acid (LNA), as well as glycol nucleic acid (GNA) and threose nucleic acid (TNA). Non-natural nucleotides can be added to one or more cycles of an amplification reaction. The addition of the non-natural nucleotides can be used to identify products as specific cycles or time points in the amplification reaction. 
     Conducting the one or more amplification reactions can comprise the use of one or more primers. The one or more primers can comprise, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 or more nucleotides. The one or more primers can comprise at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 or more nucleotides. The one or more primers can comprise less than 12-15 nucleotides. The one or more primers can anneal to at least a portion of the plurality of labeled targets (e.g., stochastically labeled targets). The one or more primers can anneal to the 3′ end or 5′ end of the plurality of labeled targets. The one or more primers can anneal to an internal region of the plurality of labeled targets. The internal region can be at least about 50, 100, 150, 200, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 650, 700, 750, 800, 850, 900 or 1000 nucleotides from the 3′ ends the plurality of labeled targets. The one or more primers can comprise a fixed panel of primers. The one or more primers can comprise at least one or more custom primers. The one or more primers can comprise at least one or more control primers. The one or more primers can comprise at least one or more gene-specific primers. 
     The one or more primers can comprise a universal primer. The universal primer can anneal to a universal primer binding site. The one or more custom primers can anneal to a first sample label, a second sample label, a spatial label, a cell label, a barcode sequence (e.g., a molecular label), a target, or any combination thereof. The one or more primers can comprise a universal primer and a custom primer. The custom primer can be designed to amplify one or more targets. The targets can comprise a subset of the total nucleic acids in one or more samples. The targets can comprise a subset of the total labeled targets in one or more samples. The one or more primers can comprise at least 96 or more custom primers. The one or more primers can comprise at least 960 or more custom primers. The one or more primers can comprise at least 9600 or more custom primers. The one or more custom primers can anneal to two or more different labeled nucleic acids. The two or more different labeled nucleic acids can correspond to one or more genes. 
     Any amplification scheme can be used in the methods of the present disclosure. For example, in one scheme, the first round PCR can amplify molecules attached to the bead using a gene specific primer and a primer against the universal Illumina sequencing primer 1 sequence. The second round of PCR can amplify the first PCR products using a nested gene specific primer flanked by Illumina sequencing primer 2 sequence, and a primer against the universal Illumina sequencing primer 1 sequence. The third round of PCR adds P 5  and P 7  and sample index to turn PCR products into an Illumina sequencing library. Sequencing using 150 bp×2 sequencing can reveal the cell label and barcode sequence (e.g., molecular label) on read 1, the gene on read 2, and the sample index on index 1 read. 
     In some embodiments, nucleic acids can be removed from the substrate using chemical cleavage. For example, a chemical group or a modified base present in a nucleic acid can be used to facilitate its removal from a solid support. For example, an enzyme can be used to remove a nucleic acid from a substrate. For example, a nucleic acid can be removed from a substrate through a restriction endonuclease digestion. For example, treatment of a nucleic acid containing a dUTP or ddUTP with uracil-d-glycosylase (UDG) can be used to remove a nucleic acid from a substrate. For example, a nucleic acid can be removed from a substrate using an enzyme that performs nucleotide excision, such as a base excision repair enzyme, such as an apurinic/apyrimidinic (AP) endonuclease. In some embodiments, a nucleic acid can be removed from a substrate using a photocleavable group and light. In some embodiments, a cleavable linker can be used to remove a nucleic acid from the substrate. For example, the cleavable linker can comprise at least one of biotin/avidin, biotin/streptavidin, biotin/neutravidin, Ig-protein A, a photo-labile linker, acid or base labile linker group, or an aptamer. 
     When the probes are gene-specific, the molecules can hybridize to the probes and be reverse transcribed and/or amplified. In some embodiments, after the nucleic acid has been synthesized (e.g., reverse transcribed), it can be amplified. Amplification can be performed in a multiplex manner, wherein multiple target nucleic acid sequences are amplified simultaneously. Amplification can add sequencing adaptors to the nucleic acid. 
     In some embodiments, amplification can be performed on the substrate, for example, with bridge amplification. cDNAs can be homopolymer tailed in order to generate a compatible end for bridge amplification using oligo(dT) probes on the substrate. In bridge amplification, the primer that is complementary to the 3′ end of the template nucleic acid can be the first primer of each pair that is covalently attached to the solid particle. When a sample containing the template nucleic acid is contacted with the particle and a single thermal cycle is performed, the template molecule can be annealed to the first primer and the first primer is elongated in the forward direction by addition of nucleotides to form a duplex molecule consisting of the template molecule and a newly formed DNA strand that is complementary to the template. In the heating step of the next cycle, the duplex molecule can be denatured, releasing the template molecule from the particle and leaving the complementary DNA strand attached to the particle through the first primer. In the annealing stage of the annealing and elongation step that follows, the complementary strand can hybridize to the second primer, which is complementary to a segment of the complementary strand at a location removed from the first primer. This hybridization can cause the complementary strand to form a bridge between the first and second primers secured to the first primer by a covalent bond and to the second primer by hybridization. In the elongation stage, the second primer can be elongated in the reverse direction by the addition of nucleotides in the same reaction mixture, thereby converting the bridge to a double-stranded bridge. The next cycle then begins, and the double-stranded bridge can be denatured to yield two single-stranded nucleic acid molecules, each having one end attached to the particle surface via the first and second primers, respectively, with the other end of each unattached. In the annealing and elongation step of this second cycle, each strand can hybridize to a further complementary primer, previously unused, on the same particle, to form new single-strand bridges. The two previously unused primers that are now hybridized elongate to convert the two new bridges to double-strand bridges. 
     The amplification reactions can comprise amplifying at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, or 100% of the plurality of nucleic acids. 
     Amplification of the labeled nucleic acids can comprise PCR-based methods or non-PCR based methods. Amplification of the labeled nucleic acids can comprise exponential amplification of the labeled nucleic acids. Amplification of the labeled nucleic acids can comprise linear amplification of the labeled nucleic acids. Amplification can be performed by polymerase chain reaction (PCR). PCR can refer to a reaction for the in vitro amplification of specific DNA sequences by the simultaneous primer extension of complementary strands of DNA. PCR can encompass derivative forms of the reaction, including but not limited to, RT-PCR, real-time PCR, nested PCR, quantitative PCR, multiplexed PCR, digital PCR, suppression PCR, semi-suppressive PCR and assembly PCR. 
     In some embodiments, amplification of the labeled nucleic acids comprises non-PCR based methods. Examples of non-PCR based methods include, but are not limited to, multiple displacement amplification (MDA), transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), strand displacement amplification (SDA), real-time SDA, rolling circle amplification, or circle-to-circle amplification. Other non-PCR-based amplification methods include multiple cycles of DNA-dependent RNA polymerase-driven RNA transcription amplification or RNA-directed DNA synthesis and transcription to amplify DNA or RNA targets, a ligase chain reaction (LCR), a Qβ replicase (%), use of palindromic probes, strand displacement amplification, oligonucleotide-driven amplification using a restriction endonuclease, an amplification method in which a primer is hybridized to a nucleic acid sequence and the resulting duplex is cleaved prior to the extension reaction and amplification, strand displacement amplification using a nucleic acid polymerase lacking 5′ exonuclease activity, rolling circle amplification, and/or ramification extension amplification (RAM). 
     In some embodiments, the methods disclosed herein further comprise conducting a nested polymerase chain reaction on the amplified amplicon (e.g., target). The amplicon can be double-stranded molecule. The double-stranded molecule can comprise a double-stranded RNA molecule, a double-stranded DNA molecule, or a RNA molecule hybridized to a DNA molecule. One or both of the strands of the double-stranded molecule can comprise a sample tag or molecular identifier label. Alternatively, the amplicon can be a single-stranded molecule. The single-stranded molecule can comprise DNA, RNA, or a combination thereof. The nucleic acids of the present invention can comprise synthetic or altered nucleic acids. 
     In some embodiments, the method comprises repeatedly amplifying the labeled nucleic acid to produce multiple amplicons. The methods disclosed herein can comprise conducting at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amplification reactions. Alternatively, the method comprises conducting at least about 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 amplification reactions. 
     Amplification can further comprise adding one or more control nucleic acids to one or more samples comprising a plurality of nucleic acids. Amplification can further comprise adding one or more control nucleic acids to a plurality of nucleic acids. The control nucleic acids can comprise a control label. 
     Amplification can comprise use of one or more non-natural nucleotides. Non-natural nucleotides can comprise photolabile and/or triggerable nucleotides. Examples of non-natural nucleotides include, but are not limited to, peptide nucleic acid (PNA), morpholino and locked nucleic acid (LNA), as well as glycol nucleic acid (GNA) and threose nucleic acid (TNA). Non-natural nucleotides can be added to one or more cycles of an amplification reaction. The addition of the non-natural nucleotides can be used to identify products as specific cycles or time points in the amplification reaction. 
     Conducting the one or more amplification reactions can comprise the use of one or more primers. The one or more primers can comprise one or more oligonucleotides. The one or more oligonucleotides can comprise at least about 7-9 nucleotides. The one or more oligonucleotides can comprise less than 12-15 nucleotides. The one or more primers can anneal to at least a portion of the plurality of labeled nucleic acids. The one or more primers can anneal to the 3′ end and/or 5′ end of the plurality of labeled nucleic acids. The one or more primers can anneal to an internal region of the plurality of labeled nucleic acids. The internal region can be at least about 50, 100, 150, 200, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 650, 700, 750, 800, 850, 900 or 1000 nucleotides from the 3′ ends the plurality of labeled nucleic acids. The one or more primers can comprise a fixed panel of primers. The one or more primers can comprise at least one or more custom primers. The one or more primers can comprise at least one or more control primers. The one or more primers can comprise at least one or more housekeeping gene primers. The one or more primers can comprise a universal primer. The universal primer can anneal to a universal primer binding site. The one or more custom primers can anneal to the first sample tag, the second sample tag, the molecular identifier label, the nucleic acid or a product thereof. The one or more primers can comprise a universal primer and a custom primer. The custom primer can be designed to amplify one or more target nucleic acids. The target nucleic acids can comprise a subset of the total nucleic acids in one or more samples. In some embodiments, the primers are the probes attached to the array of the disclosure. 
     In some embodiments, barcoding (e.g., stochastically barcoding) the plurality of targets in the sample further comprises generating an indexed library of the barcoded targets (e.g., stochastically barcoded targets) or barcoded fragments of the targets. The barcode sequences of different barcodes (e.g., the molecular labels of different stochastic barcodes) can be different from one another. Generating an indexed library of the barcoded targets includes generating a plurality of indexed polynucleotides from the plurality of targets in the sample. For example, for an indexed library of the barcoded targets comprising a first indexed target and a second indexed target, the label region of the first indexed polynucleotide can differ from the label region of the second indexed polynucleotide by, by about, by at least, or by at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, or a number or a range between any two of these values, nucleotides. In some embodiments, generating an indexed library of the barcoded targets includes contacting a plurality of targets, for example mRNA molecules, with a plurality of oligonucleotides including a poly(T) region and a label region; and conducting a first strand synthesis using a reverse transcriptase to produce single-strand labeled cDNA molecules each comprising a cDNA region and a label region, wherein the plurality of targets includes at least two mRNA molecules of different sequences and the plurality of oligonucleotides includes at least two oligonucleotides of different sequences. Generating an indexed library of the barcoded targets can further comprise amplifying the single-strand labeled cDNA molecules to produce double-strand labeled cDNA molecules; and conducting nested PCR on the double-strand labeled cDNA molecules to produce labeled amplicons. In some embodiments, the method can include generating an adaptor-labeled amplicon. 
     Barcoding (e.g., stochastic barcoding) can include using nucleic acid barcodes or tags to label individual nucleic acid (e.g., DNA or RNA) molecules. In some embodiments, it involves adding DNA barcodes or tags to cDNA molecules as they are generated from mRNA. Nested PCR can be performed to minimize PCR amplification bias. Adaptors can be added for sequencing using, for example, next generation sequencing (NGS). The sequencing results can be used to determine cell labels, molecular labels, and sequences of nucleotide fragments of the one or more copies of the targets, for example at block  232  of  FIG.  2   . 
       FIG.  3    is a schematic illustration showing a non-limiting exemplary process of generating an indexed library of the barcoded targets (e.g., stochastically barcoded targets), such as barcoded mRNAs or fragments thereof. As shown in step  1 , the reverse transcription process can encode each mRNA molecule with a unique molecular label sequence, a cell label sequence, and a universal PCR site. In particular, RNA molecules  302  can be reverse transcribed to produce labeled cDNA molecules  304 , including a cDNA region  306 , by hybridization (e.g., stochastic hybridization) of a set of barcodes (e.g., stochastic barcodes)  310  to the poly(A) tail region  308  of the RNA molecules  302 . Each of the barcodes  310  can comprise a target-binding region, for example a poly(dT) region  312 , a label region  314  (e.g., a barcode sequence or a molecule), and a universal PCR region  316 . 
     In some embodiments, the cell label sequence can include 3 to 20 nucleotides. In some embodiments, the molecular label sequence can include 3 to 20 nucleotides. In some embodiments, each of the plurality of stochastic barcodes further comprises one or more of a universal label and a cell label, wherein universal labels are the same for the plurality of stochastic barcodes on the solid support and cell labels are the same for the plurality of stochastic barcodes on the solid support. In some embodiments, the universal label can include 3 to 20 nucleotides. In some embodiments, the cell label comprises 3 to 20 nucleotides. 
     In some embodiments, the label region  314  can include a barcode sequence or a molecular label  318  and a cell label  320 . In some embodiments, the label region  314  can include one or more of a universal label, a dimension label, and a cell label. The barcode sequence or molecular label  318  can be, can be about, can be at least, or can be at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or a number or a range between any of these values, of nucleotides in length. The cell label  320  can be, can be about, can be at least, or can be at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or a number or a range between any of these values, of nucleotides in length. The universal label can be, can be about, can be at least, or can be at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or a number or a range between any of these values, of nucleotides in length. Universal labels can be the same for the plurality of stochastic barcodes on the solid support and cell labels are the same for the plurality of stochastic barcodes on the solid support. The dimension label can be, can be about, can be at least, or can be at most 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or a number or a range between any of these values, of nucleotides in length. 
     In some embodiments, the label region  314  can comprise, comprise about, comprise at least, or comprise at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or a number or a range between any of these values, different labels, such as a barcode sequence or a molecular label  318  and a cell label  320 . Each label can be, can be about, can be at least, or can be at most 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or a number or a range between any of these values, of nucleotides in length. A set of barcodes or stochastic barcodes  310  can contain, contain about, contain at least, or can be at most, 10, 20, 40, 50, 70, 80, 90, 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , 10 10 , 10 11 , 10 12 , 10 13 , 10 14 , 10 15 , 10 20 , or a number or a range between any of these values, barcodes or stochastic barcodes  310 . And the set of barcodes or stochastic barcodes  310  can, for example, each contain a unique label region  314 . The labeled cDNA molecules  304  can be purified to remove excess barcodes or stochastic barcodes  310 . Purification can comprise Ampure bead purification. 
     As shown in step  2 , products from the reverse transcription process in step  1  can be pooled into 1 tube and PCR amplified with a 1 st  PCR primer pool and a 1 st  universal PCR primer. Pooling is possible because of the unique label region  314 . In particular, the labeled cDNA molecules  304  can be amplified to produce nested PCR labeled amplicons  322 . Amplification can comprise multiplex PCR amplification. Amplification can comprise a multiplex PCR amplification with 96 multiplex primers in a single reaction volume. In some embodiments, multiplex PCR amplification can utilize, utilize about, utilize at least, or utilize at most, 10, 20, 40, 50, 70, 80, 90, 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , 10 10 , 10 11 , 10 12 , 10 13 , 10 14 , 10 15 , 10 20 , or a number or a range between any of these values, multiplex primers in a single reaction volume. Amplification can comprise using a 1 st  PCR primer pool  324  comprising custom primers  326 A-C targeting specific genes and a universal primer  328 . The custom primers  326  can hybridize to a region within the cDNA portion  306 ′ of the labeled cDNA molecule  304 . The universal primer  328  can hybridize to the universal PCR region  316  of the labeled cDNA molecule  304 . 
     As shown in step  3  of  FIG.  3   , products from PCR amplification in step  2  can be amplified with a nested PCR primers pool and a 2 nd  universal PCR primer. Nested PCR can minimize PCR amplification bias. In particular, the nested PCR labeled amplicons  322  can be further amplified by nested PCR. The nested PCR can comprise multiplex PCR with nested PCR primers pool  330  of nested PCR primers  332   a - c  and a 2 nd  universal PCR primer  328 ′ in a single reaction volume. The nested PCR primer pool  328  can contain, contain about, contain at least, or contain at most, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or a number or a range between any of these values, different nested PCR primers  330 . The nested PCR primers  332  can contain an adaptor  334  and hybridize to a region within the cDNA portion  306 ″ of the labeled amplicon  322 . The universal primer  328 ′ can contain an adaptor  336  and hybridize to the universal PCR region  316  of the labeled amplicon  322 . Thus, step  3  produces adaptor-labeled amplicon  338 . In some embodiments, nested PCR primers  332  and the 2 nd  universal PCR primer  328 ′ may not contain the adaptors  334  and  336 . The adaptors  334  and  336  can instead be ligated to the products of nested PCR to produce adaptor-labeled amplicon  338 . 
     As shown in step  4 , PCR products from step  3  can be PCR amplified for sequencing using library amplification primers. In particular, the adaptors  334  and  336  can be used to conduct one or more additional assays on the adaptor-labeled amplicon  338 . The adaptors  334  and  336  can be hybridized to primers  340  and  342 . The one or more primers  340  and  342  can be PCR amplification primers. The one or more primers  340  and  342  can be sequencing primers. The one or more adaptors  334  and  336  can be used for further amplification of the adaptor-labeled amplicons  338 . The one or more adaptors  334  and  336  can be used for sequencing the adaptor-labeled amplicon  338 . The primer  342  can contain a plate index  344  so that amplicons generated using the same set of barcodes or stochastic barcodes  310  can be sequenced in one sequencing reaction using next generation sequencing (NGS). 
     Barcoding on 5′ Ends of Nucleic Acid Targets 
     Disclosed herein includes systems, methods, compositions, and kits for attachment of barcodes (e.g., stochastic barcodes) with molecular labels (or molecular indices) to the 5′-ends of nucleic acid targets being barcoded or labeled (e.g., deoxyribonucleic acid molecules, and ribonucleic acid molecules). The 5′-based transcript counting methods disclosed herein can complement, or supplement, for example, 3′-based transcript counting methods (e.g., Rhapsody™ assay (Becton, Dickinson and Company (Franklin Lakes, N.J.)), Chromium™ Single Cell 3′ Solution (10× Genomics (San Francisco, Calif.))). The barcoded nucleic acid targets can be used for sequence identification, transcript counting, alternative splicing analysis, mutation screening, and/or full length sequencing in a high throughput manner. Transcript counting on the 5′-end (5′ relative to the target nucleic acid targets being labeled) can reveal alternative splicing isoforms and variants (including, but not limited to, splice variants, single nucleotide polymorphisms (SNPs), insertions, deletions, substitutions.) on, or closer to, the 5′-ends of nucleic acid molecules. In some embodiments, the method can involve intramolecular hybridization. 
       FIGS.  4 A- 4 B  show a schematic illustration of a non-limiting exemplary method  400  of gene-specific labeling nucleic acid targets on the 5′-ends. A barcode  420  (e.g., a stochastic barcode) with a target binding region (e.g., a poly(dT) tail  422 ) can bind to poly-adenylated RNA transcripts  424  via the poly(dA) tail  426 , or other nucleic acid targets, for labeling or barcoding (e.g., unique labeling). The barcodes  420  can include molecular labels (MLs)  428  and sample labels (SLs)  430  for labeling the transcripts  424  and tracking sample origins of the RNA transcripts  424 , respectively, along with one or more additional sequences (e.g., consensus sequences, such as an adaptor sequence  432 ), flanking the molecular label  428 /sample label  430  region of each barcode  420  for subsequent reactions. The repertoire of sequences of the molecular labels in the barcodes per sample can be sufficiently large for stochastic labeling of RNA transcripts. 
     After cDNA synthesis at block  402  to generate barcoded cDNA molecules  434  comprising the RNA transcripts  424  (or a portion thereof), a gene specific method can be used for 5′ molecular barcoding. After gene specific amplification at block  404 , which can be optional, a terminal transferase and deoxyadenosine triphosphates (dATPs) can be added at block  406  to facilitate 3′ poly(dA) tailing to generate amplicons  436  with a poly(A) tail  438 . A short denaturation step at block  408  allows the separation of forward  436   m  and reverse strands  436   c  (e.g., barcoded cDNA molecules with poly(dA) tails) of the amplicon  436 . The reverse strand  436   c  of the amplicon  436  can hybridize intra-molecularly via its poly(dA) tail  438  on the 3′ end and the poly(dT) region  422  end of the strand to form a hairpin or stem loop  440  at block  410 . An polymerase (e.g., a Klenow fragment) can then be used to extend from the poly(dA) tail  438  to duplicate the barcode to form extended barcoded reverse strand  442  at block  412 . Gene specific amplification at block  414  (e.g., optionally) can then be performed to amplify genes of interest to produce amplicons  444  with barcodes on the 5′ end (relative to the RNA transcripts  424 ) for sequencing at block  416 . In some embodiments, the method  400  includes one or both of gene specific amplification of barcoded cDNA molecule  434  at block  404  and gene specific amplification of extended barcoded reverse strand  442  at block  414 . 
       FIGS.  5 A- 5 B  show a schematic illustration of a non-limiting exemplary method  500  of labeling nucleic acid targets on the 5′-ends for whole transcriptome analysis. A barcode  420  (e.g., a stochastic barcode) with a target binding region (e.g., a poly(dT) tail  422 ) can bind to poly-adenylated RNA transcripts  424  via the poly(dA) tail  426 , or other nucleic acid targets, for labeling or barcoding (e.g., unique labeling). For example, a barcode  420  with a target binding region can bind to a nucleic acid target for labeling or barcoding. A barcode  420  can include a molecular label (ML)  428  and a sample label (SL)  430 . Molecular labels  428  and sample labels  430  can be used for labeling the transcripts  424 , or nucleic acid targets (e.g., antibody oligonucleotides, whether associated with antibodies or have dissociated from antibodies) and tracking sample origins of the transcripts  424 , respectively, along with one or more additional sequences (e.g., consensus sequences, such as an adaptor sequence  432 ), flanking the molecular label  428 /sample label  430  region of each barcode  420  for subsequent reactions. The repertoire of sequences of the molecular labels  428  in the barcodes per sample can be sufficiently large for stochastic labeling of RNA transcripts  424 , or nucleic acid targets. 
     After cDNA synthesis to generate barcoded cDNA molecules  434  at block  402 , a terminal transferase enzyme can be used for A-tailing of the 3′ end of the barcoded cDNA molecules  434  (equivalent to the 5′ end of RNA transcripts labeled) to generate cDNA molecules  436   c  each with a 3′ poly(dA) tail  438  at block  406 . Intramolecular hybridization of the cDNA molecules  436   c  with 3′ poly(dA) tails  438  can be initiated (e.g., with a heat and cooling cycle, or by diluting the barcoded cDNA molecules  436   c  with poly(dA) tails  438 ) such that the new 3′ poly(dA) tail  438  is annealed with the poly(dT) tail  422  of the same labeled cDNA molecule to generate a barcoded cDNA molecule a hairpin or stem loop structure  440  at block  410 . A polymerase (e.g., Klenow enzyme) with dNTP can be added to facilitate a 3′ extension beyond the new 3′ poly(dA) tail  438  to duplicate the barcodes (e.g., molecular labels  428  that are on the 5′-ends of the labeled cDNA molecules with stem loops  440  at block  412 . A whole transcriptome amplification (WTA) can be performed at block  414  using mirrored adaptors  432 ,  432   rc  or primers containing sequences (or subsequences) of the adaptors  432 ,  432   rc . Methods, such as tagmentation or random priming, can be used to generate smaller fragments of amplicons  444  with sequencing adaptors (e.g., P 5   446  and P 7   448  sequence) for sequencing at block  418  (e.g., using an Illumina (San Diego, Calif., U.S.) sequencer). In some embodiments, sequencing adaptors for other sequencing methods or sequencers (e.g., sequencers from Pacific Biosciences of California, Inc. (Menlo Park, Calif., US) or Oxford Nanopore Technologies Limited (Oxford, UK)) can be directly ligated to generate amplicons for sequencing. 
     Disclosed herein includes methods for determining the numbers of a nucleic acid target in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target  424  in a sample to a plurality of oligonucleotide barcodes  420 , wherein each of the plurality of oligonucleotide barcodes  420  comprises a molecular label sequence  428  and a target-binding region (e.g., a poly(dT) sequence  422 ) capable of hybridizing to the nucleic acid target  424 , and wherein at least 10 of the plurality of oligonucleotide barcodes  420  comprise different molecular label sequences  428 ; extending the copies of the nucleic acid target  424  hybridized to the oligonucleotide barcodes  420  to generate a plurality of nucleic acid molecules  434  each comprising a sequence complementary  450   c  to at least a portion of the nucleic acid target  424  at block  402 ; amplifying the plurality of barcoded nucleic acid molecules  434  at block  404  to generate a plurality of amplified barcoded nucleic acid molecules  436 ; attaching an oligonucleotide comprising the complement  438  of the target-binding region  422  to the plurality of amplified barcoded nucleic acid molecules  436  to generate a plurality of barcoded nucleic acid molecules  436   c  each comprising the target-binding region  422  and a complement  438  of the target-binding region at block  406 ; hybridizing the target-binding region  422  and the complement  438  of the target-binding region  422  within each of the plurality of barcoded nucleic acid molecules  436   c  to form a stem loop  440  at block  410 ; extending 3′-ends of the plurality of barcoded nucleic acid molecules each with the stem loop  440  at block  412  to extend the stem loop  440  to generate a plurality of extended barcoded nucleic acid molecules  442  each comprising the molecular label  428  and a complement  428   rc  of the molecular label; amplifying the plurality of extended barcoded nucleic acid molecules  442  at block  414  to generate a plurality of single-labeled nucleic acid molecules  444   c  each comprising the complement  428   rc  of the molecular label; and determining the number of the nucleic acid target in the sample based on the number of complements  428   rc  of molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. 
     In some embodiments, the molecular label  428  is hybridized to the complement  428   rc  of the molecular label after extending the 3′-ends of the plurality of barcoded nucleic acid molecules with the stem loops  440 . The method can comprise denaturing the plurality of extended barcoded nucleic acid molecules  442  prior to amplifying the plurality of extended barcoded nucleic acid molecules  442  to generate the plurality of single-labeled nucleic acid molecules  444   c  (which can be part of the amplicons  444   c ). Contacting copies of the nucleic acid target  424  in the sample can comprise contacting copies of a plurality of nucleic acid targets  424  to a plurality of oligonucleotide barcodes  420 . Extending the copies of the nucleic acid target  424  can comprise extending the copies of the plurality nucleic acid targets  424  hybridized to the oligonucleotide barcodes  420  to generate a plurality of barcoded nucleic acid molecules  436   c  each comprising a sequence complementary  450   c  to at least a portion of one of the plurality of nucleic acid targets  424 . Determining the number of the nucleic acid target  424  can comprise determining the number of each of the plurality of nucleic acid targets  424  in the sample based on the number of the complements  428   rc  of the molecular labels with distinct sequences associated with single-labeled nucleic acid molecules of the plurality of single-labeled nucleic acid molecules  444   c  comprising a sequence  452   c  of the each of the plurality of nucleic acid targets  424 . The sequence  452   c  of the each of the plurality of nucleic acid targets can comprise a subsequence (including a complement or a reverse complement) of the each of the plurality of nucleic acid targets  424 . 
     Disclosed herein includes methods for determining the numbers of targets in a sample. In some embodiments, the method comprises: barcoding  402  copies of a nucleic acid target  424  in a sample using a plurality of oligonucleotide barcodes  420  to generate a plurality of barcoded nucleic acid molecules  434  each comprising a sequence  450   c  (e.g., a complementary sequence, a reverse complementary sequence, or a combination thereof) of the nucleic acid target  424 , a molecular label  428 , and a target-binding region (e.g., a poly(dT) region  422 ), and wherein at least 10 of the plurality of oligonucleotide barcodes  420  comprise different molecular label sequences  428 ; attaching  406  an oligonucleotide comprising a complement  438  of the target-binding region  422  to the plurality of barcoded nucleic acid molecules  434  to generate a plurality of barcoded nucleic acid molecules  436  each comprising the target-binding region  422  and the complement  438  of the target-binding region  422 ; hybridizing  410  the target-binding region  422  and the complement  438  of the target-binding region within each of the plurality of barcoded nucleic acid molecules  436   c  to form a stem loop  440 ; extending  412  3′-ends of the plurality of barcoded nucleic acid molecules to extend the stem loop  440  to generate a plurality of extended barcoded nucleic acid molecules  442  each comprising the molecular label  428  and a complement  428   rc  of the molecular label; and determining the number of the nucleic acid target  424  in the sample based on the number of complements  428   rc  of molecular labels with distinct sequences associated with the plurality of extended barcoded nucleic acid molecules  442 . 
     Disclosed herein includes methods for attaching oligonucleotide barcodes to a target in a sample. In some embodiments, the method comprises: barcoding  402  copies of a nucleic acid target  424  in a sample using a plurality of oligonucleotide barcodes  420  to generate a plurality of barcoded nucleic acid molecules  434  each comprising a sequence  450   c  of the nucleic acid target  424 , a molecular label  428 , and a target-binding region  422 , and wherein at least 10 of the plurality of oligonucleotide barcodes  420  comprise different molecular label sequences  428 ; attaching an oligonucleotide comprising a complement  438  of the target binding region  422  to the plurality of barcoded nucleic acid molecules  434  to generate a plurality of barcoded nucleic acid molecules  436   c  each comprising the target-binding region  422  and the complement  438  of the target-binding region  422 ; hybridizing  410  the target-binding region  422  and the complement  438  of the target-binding region  422  within each of the plurality of barcoded nucleic acid molecules  436   c  to form a stem loop  440 ; and extending  412  3′-ends of the plurality of barcoded nucleic acid molecules to extend the stem loop  440  to generate a plurality of extended barcoded nucleic acid molecules  442  each comprising the molecular label  428  and a complement  428   rc  of the molecular label  428 . In some embodiments, the method comprises: determining the number of the nucleic acid target  424  in the sample based on the number of molecular labels  428  with distinct sequences, complements  428   rc  thereof, or a combination thereof, associated with the plurality of extended barcoded nucleic acid molecules  442 . For example, the number of the nucleic acid target  424  can be determined based on one or both of the molecular labels  428  with distinct sequences, complements  428   rc  thereof. 
     In some embodiments, the method comprises: barcoding  402  the copies of the plurality of targets  424  comprises: contacting copies of the nucleic acid target  424  to the plurality of oligonucleotide barcodes  420 , wherein each of the plurality of oligonucleotide barcodes  420  comprises the target-binding region  422  capable of hybridizing to the nucleic acid target  424 ; and extending  402  the copies of the nucleic acid target  424  hybridized to the oligonucleotide barcodes  420  to generate the plurality of barcoded nucleic acid molecules  434 . 
     In some embodiments, the method comprises: amplifying  404  the plurality of barcoded nucleic acid molecules  434  to generate a plurality of amplified barcoded nucleic acid molecules  436   c , wherein attaching the oligonucleotide comprising the complement  438  of the target-binding region  422  comprises: attaching the oligonucleotide comprising the complement  438  of the target binding region to the plurality of amplified barcoded nucleic molecules to generate a plurality of barcoded nucleic acid molecules  436   r  each comprising the target-binding region  422  and a complement  438  of the target-binding region. 
     Gene Specific Analysis. In some embodiments, the method (e.g., the method  400 ) comprises: amplifying  414  the plurality of extended barcoded nucleic acid molecules  442  to generate a plurality of single-labeled nucleic acid molecules  444   c  each comprising the complement  428   rc  of the molecular label  428 . The single-labeled nucleic acid molecules  444   c  can be generated when the amplicons  444  containing them are denatured. Determining the number of the nucleic acid target  424  in the sample can comprise: determining the number of the nucleic acid target  424  in the sample based on the number of complements  428   rc  of molecular labels  428  with distinct sequences associated with the plurality of single-labeled nucleic acid molecules  444   c.    
     Whole Transcriptome Analysis. In some embodiments, the method (e.g., the method  500 ) comprises: amplifying  414  the plurality of extended barcoded nucleic acid molecules  442  to generate copies  444   c  of the plurality of extended barcoded nucleic acid molecules. Determining the number of the nucleic acid target  424  in the sample comprises: determining the number of the nucleic acid target  424  in the sample based on the number of complements  428   rc  of molecular labels  428  with distinct sequences associated with the copies  444   c  of plurality of extended barcoded nucleic acid molecules. The copies  444   c  of the plurality of extended barcoded nucleic acid molecules can be formed when amplicons  444  containing them are denatured. 
     In some embodiments, the sequence of the nucleic acid target in the plurality of barcoded nucleic acid molecules comprises a subsequence  452   c  of the nucleic acid target. The target-binding region can comprise a gene-specific sequence. Attaching  406  the oligonucleotide comprising the complement  438  of the target binding region  422  can comprise ligating the oligonucleotide comprising the complement  438  of the target binding region  422  to the plurality of barcoded nucleic acid molecules  434 . 
     In some embodiments, the target-binding region can comprise a poly(dT) sequence  422 . Attaching the oligonucleotide comprising the complement  438  of the target binding region  422  comprises: adding a plurality of adenosine monophosphates to the plurality of barcoded nucleic acid molecules  434  using a terminal deoxynucleotidyl transferase. 
     In some embodiments, extending the copies of the nucleic acid target  424  hybridized to the oligonucleotide barcodes  420  can comprise reverse transcribing the copies of the nucleic acid target  424  hybridized to the oligonucleotide barcodes  420  to generate a plurality of barcoded complementary deoxyribonucleic acid (cDNA) molecules  434 . Extending the copies of the nucleic acid target  424  hybridized to the oligonucleotide barcodes  420  can comprise extending  402  the copies of the nucleic acid target  424  hybridized to the oligonucleotide barcodes  420  using a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity. The DNA polymerase can comprise a Klenow Fragment. 
     In some embodiments, the method comprises: obtaining sequence information of the plurality of extended barcoded nucleic acid molecules  442 . Obtaining the sequence information can comprise attaching sequencing adaptors (e.g., the P 5   446  and P 7   448  adaptor) to the plurality of extended barcoded nucleic acid molecules  442 . 
     In some embodiments, the complement  438  of the target-binding region can comprise the reverse complementary sequence of the target-binding region. The complement  438  of the target-binding region can comprise the complementary sequence of the target-binding region. The complement  428   rc  of the molecular label can comprise a reverse complementary sequence of the molecular label. The complement of the molecular label can comprise a complementary sequence of the molecular label. 
     In some embodiments, the plurality of barcoded nucleic acid molecules  434  can comprise barcoded deoxyribonucleic acid (DNA) molecules. The barcoded nucleic acid molecules  434  can comprise barcoded ribonucleic acid (RNA) molecules. The nucleic acid target  424  can comprise a nucleic acid molecule. The nucleic acid molecule can comprise ribonucleic acid (RNA), messenger RNA (mRNA), microRNA, small interfering RNA (siRNA), RNA degradation product, RNA comprising a poly(A) tail, or any combination thereof. 
     Antibody Oligonucleotides. In some embodiments, the nucleic acid target can comprise a cellular component binding reagent. Cellular binding reagents associated with nucleic acid targets (e.g., antibody oligonucleotides, such as sample indexing oligonucleotides) have been described in US2018/0088112; and U.S. application Ser. No. 15/937,713, filed on Mar. 27, 2018; the content of each of these applications is incorporated herein by reference in its entirety. In some embodiments, multiomics information, such as genomics, chromatin accessibility, methylomics, transcriptomics, and proteomics, of single cells can be obtained using 5′ barcoding methods of the disclosure. The nucleic acid molecule can be associated with the cellular component binding reagent. The method can comprise dissociating the nucleic acid molecule and the cellular component binding reagent. 
     In some embodiments, each molecular label  428  of the plurality of oligonucleotide barcodes  420  comprises at least 6 nucleotides. The oligonucleotide barcode  420  can comprise an identical sample label  430 . Each sample label  430  of the plurality of oligonucleotide barcodes  420  can comprise at least 6 nucleotides. The oligonucleotide barcode  420  can comprise an identical cell label. Each cell label of the plurality of oligonucleotide barcodes  420  can comprise at least 6 nucleotides. 
     In some embodiments, at least one of the plurality of barcoded nucleic acid molecules  436   c  is associated with a solid support when hybridizing  410  the target-binding region and the complement of the target-binding region within each of the plurality of barcoded nucleic acid molecules to form the stem loop. At least one of the plurality of barcoded nucleic acid molecules  436   c  can dissociate from a solid support when hybridizing  410  the target-binding region  422  and the complement  438  of the target-binding region  422  within each of the plurality of barcoded nucleic acid molecules  436   c  to form the stem loop  440 . At least one of the plurality of barcoded nucleic acid molecules  436   c  can be associated with a solid support when hybridizing  410  the target-binding region  422  and the complement  438  of the target-binding region within each of the plurality of barcoded nucleic acid molecules  436   c  to form the stem loop  440 . 
     In some embodiments, at least one of the plurality of barcoded nucleic acid molecules is associated with a solid support when extending  412  the 3′-ends of the plurality of barcoded nucleic acid molecules to extend the stem loop  440  to generate the plurality of extended barcoded nucleic acid molecules  442  each comprising the molecular label  428  and a complement  428   rc  of the molecular label. At least one of the plurality of barcoded nucleic acid molecules can dissociate from a solid support when extending  412  the 3′-ends of the plurality of barcoded nucleic acid molecules to extend the stem loop  440  to generate the plurality of extended barcoded nucleic acid molecules  442  each comprising the molecular label  428  and a complement  428   rc  of the molecular label. At least one of the plurality of barcoded nucleic acid molecules  436   c  can be associated with a solid support when extending  412  the 3′-ends of the plurality of barcoded nucleic acid molecules to extend the stem loop  440  to generate the plurality of extended barcoded nucleic acid molecules  442  each comprising the molecular label  428  and a complement  428   rc  of the molecular label. The solid support can comprise a synthetic particle  454 . The solid support can comprise a planar surface or a substantially planar surface (e.g., a slide, such as a microscope slide or a coverslip). 
     In some embodiments, at least one of the plurality of barcoded nucleic acid molecules  436   c  is in solution when hybridizing  410  the target-binding region  422  and the complement  438  of the target-binding region  422  within each of the plurality of barcoded nucleic acid molecules  436   c  to form the stem loop  440 . For example, when the concentration of the plurality of barcoded nucleic acid molecules  436   c  in solution is sufficiently low, such intra-molecular hybridization can occur. At least one of the plurality of barcoded nucleic acid molecules can be in solution when extending  412  the 3′-ends of the plurality of barcoded nucleic acid molecules to extend the stem loop  440  to generate the plurality of extended barcoded nucleic acid molecules  442  each comprising the molecular label  428  and a complement  428   rc  of the molecular label. 
     In some embodiments, the sample comprises a single cell, the method comprising associating a synthetic particle  454  comprising the plurality of the oligonucleotide barcodes  420  with the single cell in the sample. The method can comprise: lysing the single cell after associating the synthetic particle  454  with the single cell. Lysing the single cell can comprise heating the sample, contacting the sample with a detergent, changing the pH of the sample, or any combination thereof. The synthetic particle and the single cell can be in the same well. The synthetic particle and the single cell can be in the same droplet. 
     In some embodiments, at least one of the plurality of oligonucleotide barcodes  420  can be immobilized on the synthetic particle  454 . At least one of the plurality of oligonucleotide barcodes  420  can be partially immobilized on the synthetic particle  454 . At least one of the plurality of oligonucleotide barcodes  420  can be enclosed in the synthetic particle  454 . At least one of the plurality of oligonucleotide barcodes  420  can be partially enclosed in the synthetic particle  454 . The synthetic particle  454  can be disruptable. The synthetic particle  454  can comprise a bead. The bead can comprise a Sepharose bead, a streptavidin bead, an agarose bead, a magnetic bead, a conjugated bead, a protein A conjugated bead, a protein G conjugated bead, a protein A/G conjugated bead, a protein L conjugated bead, an oligo(dT) conjugated bead, a silica bead, a silica-like bead, an anti-biotin microbead, an anti-fluorochrome microbead, or any combination thereof. The synthetic particle  454  can comprise a material selected from the group consisting of polydimethylsiloxane (PDMS), polystyrene, glass, polypropylene, agarose, gelatin, hydrogel, paramagnetic, ceramic, plastic, glass, methylstyrene, acrylic polymer, titanium, latex, Sepharose, cellulose, nylon, silicone, and any combination thereof. The synthetic particle  454  can comprise a disruptable hydrogel particle. Each of the plurality of oligonucleotide barcodes  420  can comprise a linker functional group. The synthetic particle  454  can comprise a solid support functional group. The support functional group and the linker functional group can be associated with each other. The linker functional group and the support functional group can be individually selected from the group consisting of C6, biotin, streptavidin, primary amine(s), aldehyde(s), ketone(s), and any combination thereof. 
     Kits for Barcoding on 5′ Ends of Nucleic Acid Targets 
     Disclosed herein includes kits for attaching oligonucleotide barcodes  420  to a target  424  in a sample, determining the numbers of targets  424  in a sample, and/or determining the numbers of a nucleic acid target  424  in a sample. In some embodiments, the kit includes: a plurality of oligonucleotide barcodes  420 , wherein each of the plurality of oligonucleotide barcodes  420  comprises a molecular label  428  and a target-binding region (e.g., a poly(dT) sequence  422 ), and wherein at least 10 of the plurality of oligonucleotide barcodes  420  comprise different molecular label sequences  428 ; a terminal deoxynucleotidyl transferase or a ligase; and a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity. The DNA polymerase can comprise a Klenow Fragment. The kit can comprise a buffer. The kit can comprise a cartridge. The kit can comprise one or more reagents for a reverse transcription reaction. The kit can comprise one or more reagents for an amplification reaction. 
     In some embodiments, the target-binding region comprises a gene-specific sequence, an oligo(dT) sequence, a random multimer, or any combination thereof. The oligonucleotide barcode can comprise an identical sample label and/or an identical cell label. Each sample label and/or cell label of the plurality of oligonucleotide barcodes can comprise at least 6 nucleotides. Each molecular label of the plurality of oligonucleotide barcodes can comprise at least 6 nucleotides. 
     In some embodiments, at least one of the plurality of oligonucleotide barcodes  420  is immobilized on the synthetic particle  454 . At least one of the plurality of oligonucleotide barcodes  420  can be partially immobilized on the synthetic particle  454 . At least one of the plurality of oligonucleotide barcodes  420  can be enclosed in the synthetic particle  454 . At least one of the plurality of oligonucleotide barcodes  420  can be partially enclosed in the synthetic particle  454 . The synthetic particle  454  can be disruptable. The synthetic particle  454  can comprise a bead. The bead can comprise a Sepharose bead, a streptavidin bead, an agarose bead, a magnetic bead, a conjugated bead, a protein A conjugated bead, a protein G conjugated bead, a protein A/G conjugated bead, a protein L conjugated bead, an oligo(dT) conjugated bead, a silica bead, a silica-like bead, an anti-biotin microbead, an anti-fluorochrome microbead, or any combination thereof. The synthetic particle can comprise a material selected from the group consisting of polydimethylsiloxane (PDMS), polystyrene, glass, polypropylene, agarose, gelatin, hydrogel, paramagnetic, ceramic, plastic, glass, methylstyrene, acrylic polymer, titanium, latex, Sepharose, cellulose, nylon, silicone, and any combination thereof. The synthetic particle  454  can comprise a disruptable hydrogel particle. Each of the plurality of oligonucleotide barcodes can comprise a linker functional group. The synthetic particle  454  can comprise a solid support functional group. The support functional group and the linker functional group can be associated with each other. The linker functional group and the support functional group can be individually selected from the group consisting of C6, biotin, streptavidin, primary amine(s), aldehyde(s), ketone(s), and any combination thereof. 
     Determining 5′ Transcript Sequences 
     High-throughput single-cell RNA-sequencing has transformed the understanding of complex and heterogenous biological samples. However, most methods enable only 3′ analysis of the mRNA transcript information, which may limit analysis of splice variants, alternative transcription start sites and highly variable loci due to rearrangement such as the VDJ junction of T cell and B cell receptors and antibodies. As disclosed herein, mRNA molecules were captured and sequencing libraries were generated for both 3′ and 5′ end of transcripts in a high-throughput manner using the BD Rhapsody platform. 
     The methods of the disclosure can be used for identifying VDJ regions of B cell receptors (BCR), T cell receptors (TCR), and antibodies. VDJ recombination, also known as somatic recombination, is a mechanism of genetic recombination in the early stages of immunoglobulin (Ig) (e.g., BCR) and T cell receptor (TCR) production of the immune system. VDJ recombination can nearly randomly combine Variable (V), Diverse (D) and Joining (J) gene segments. Because of its randomness in choosing different genes, it is able to diversely encode proteins to match antigens from bacteria, viruses, parasites, dysfunctional cells such as tumor cells and pollens. 
     The VDJ region can comprise a large 3 Mb locus comprising variable (V) genes, diversity (D) genes and joining (J) genes. These are the segments that can participate in VDJ recombination. There can be constant genes which may not undergo VDJ recombination. The first event in the VDJ recombination of this locus can be that one of the D genes rearranges to one of the J genes. Following this, one of the V genes can be appended to this DJ rearrangement to form the functional VDJ rearranged gene that then codes for the variable segment of the heavy chain protein. Both of these steps can be catalyzed by recombinase enzymes, which can delete out the intervening DNA. 
     This recombination process takes place in a stepwise fashion in progenitor B cells to produce the diversity required for the antibody repertoire. Each B cell may only produce one antibody (e.g., BCR). This specificity can be achieved by allelic exclusion such that functional rearrangement of one allele signals to prevent further recombination of the second allele. 
     In some embodiments, the sample comprises an immune cell. An immune cell can include, for example, T cell, B cell, lymphoid stem cell, myeloid progenitor cell, lymphocyte, granulocyte, B-cell progenitor, T cell progenitor, Natural Killer cell, Tc cell, Th cell, plasma cell, memory cell, neutrophil, eosinophil, basophil, mast cell, monocyte, dendritic cell and/or macrophage, or any combination thereof. 
     A T cell can be a T cell clone, which can refer to T cells derived from a single T cell or those having identical TCRs. A T cell can be part of a T cell line which can include T cell clones and mixed populations of T cells with different TCRs all of which may recognize the same target (e.g., antigen, tumor, virus). T cells can be obtained from a number of sources, including peripheral blood mononuclear cells, bone marrow, lymph node tissue, spleen tissue, and tumors. T cells can be obtained from a unit of blood collected from a subject, such as using the Ficoll separation. Cells from the circulating blood of an individual can be obtained by apheresis or leukapheresis. The apheresis product can comprise lymphocytes, including T cells, monocytes, granulocytes, B cells, other nucleated white blood cells, red blood cells, and platelets. The cells can be washed and resuspended in media to isolate the cell of interest. 
     T cells can be isolated from peripheral blood lymphocytes by lysing the red blood cells and depleting the monocytes, for example, by centrifugation through a PERCOLL™ gradient. A specific subpopulation of T cells, such as CD28+, CD4+, CDC, CD45RA+, and CD45RO+ T cells, can be further isolated by positive or negative selection techniques. For example, T cells can be isolated by incubation with anti-CD3/anti-CD28 (i.e., 3×28)-conjugated beads, such as DYNABEADS® M-450 CD3/CD28 T, or XCYTE DYNABEADS™ for a time period sufficient for positive selection of the desired T cells. Immune cells (e.g., T cells and B cells) can be antigen specific (e.g., specific for a tumor). 
     In some embodiments, the cell can be an antigen-presenting cell (APC), such as a B cell, an activated B cell from a lymph node, a lymphoblastoid cell, a resting B-cell, or a neoplastic B cell, e.g. from a lymphoma. An APC can refer to a B-cell or a follicular dendritic cell expressing at least one of the BCRC proteins on its surface. 
     The methods of the disclosure can be used to trace the molecular phenotype of single T cells. Different subtypes of T cells can be distinguished by expression of different molecular markers. T cells express a unique T cell receptor (TCR) from a diverse repertoire of TCRs. In most T cells, the TCR can be composed of a heterodimer of a α and a β chain; each functional chain can be a product of somatic DNA recombination events during T cell development, allowing the expression of over a million different TCRs in a single individual. TCRs can be used to define the identity of individual T cells, allowing for lineage tracing for T cell clonal expansion during an immune response. The immunological methods of the disclosure can be used in a variety of ways, including but not limited to, identifying unique TCRα and TCRβ chain pairing in single T cells, quantifying TCR and marker expression at the single cell level, identifying TCR diversity in an individual, characterizing the TCR repertoire expressed in different T cell populations, determining functionality of the alpha and beta chain alleles of the TCR, and identifying clonal expansion of T cells during immune response. 
     T-Cell Receptor Chain Pairing 
     T-cell receptors (TCRs) are recognition molecules present on the surface of T lymphocytes. The T-cell receptors found on the surface of T-cells can be comprised of two glycoprotein subunits which are referred to as the alpha and beta chains. Both chains can comprise a molecular weight of about 40 kDa and possess a variable and a constant domain. The genes which encode the alpha and beta chains can be organized in libraries of V, D and J regions from which the genes are formed by genetic rearrangement. TCRs can recognize antigen which is presented by an antigen presenting cell as a part of a complex with a specific self-molecule encoded by a histocompatibility gene. The most potent histocompatibility genes are known as the major histocompatibility complex (MHC). The complex which is recognized by T-cell receptors, therefore, consists of and MHC/peptide ligand. 
     In some embodiments, the methods, devices, and systems of the disclosure can be used for T cell receptor sequencing and pairing. The methods, devices, and systems of the disclosure can be used for sequencing T-cell receptor alpha and beta chains, pairing alpha and beta chains, and/or determining the functional copy of T-cell receptor alpha chains. A single cell can be contained in a single partition (e.g., well) with a single solid support (e.g., bead). The cell can be lysed. The bead can comprise a stochastic label that can bind to a specific location within an alpha and/or beta chain of a TCR. The TCR alpha and beta molecules associated with solid support can be subjected to the molecular biology methods of the disclosure, including reverse transcription, amplification, and sequencing. TCR alpha and beta chains that comprise the same cellular label can be considered to be from the same single cell, thereby pairing alpha and beta chains of the TCR. 
     Heavy and Light Chain Pairing in Antibody Repertoires 
     The methods devices and systems of the disclosure can be used for heavy and light chain pairing of BCR receptors and antibodies. The methods of the present disclosure allow for the repertoire of immune receptors and antibodies in an individual organism or population of cells to be determined. The methods of the present disclosure may aid in determining pairs of polypeptide chains that make up immune receptors. B cells and T cells each express immune receptors; B cells express immunoglobulins and BCRs, and T cells express T cell receptors (TCRs). Both types of immune receptors can comprise two polypeptide chains. Immunoglobulins can comprise variable heavy (VH) and variable light (VL) chains. There can be two types of TCRs: one consisting of an alpha and a beta chain, and one consisting of a delta and a gamma chain. Polypeptides in an immune receptor can comprise constant region and a variable region. Variable regions can result from recombination and end joint rearrangement of gene fragments on the chromosome of a B or T cell. In B cells additional diversification of variable regions can occur by somatic hypermutation. 
     The immune system has a large repertoire of receptors, and any given receptor pair expressed by a lymphocyte can be encoded by a pair of separate, unique transcripts. Knowing the sequences of pairs of immune receptor chains expressed in a single cell can be used to ascertain the immune repertoire of a given individual or population of cells. 
     In some embodiments, the methods, devices, and systems of the disclosure can be used for antibody sequencing and pairing. The methods, devices, and systems of the disclosure can be used for sequencing antibody heavy and light chains (e.g., in B cells), and/or pairing the heavy and light chains. A single cell can be contained in a single partition (e.g., well) with a single solid support (e.g., bead). The cell can be lysed. 
     The bead can comprise a stochastic label that can bind to a specific location within a heavy and/or light chain of an antibody (e.g., in a B cell). The heavy and light chain molecules associated with solid support can be subjected to the molecular biology methods of the disclosure, including reverse transcription, amplification, and sequencing. Antibody heavy and light chains that comprise the same cellular label can be considered to be from the same single cell, thereby pairing heavy and light chains of the antibody. 
     There are provided, in some embodiments, primer panels for the identification and quantification of human and mouse immune repertoire variable domain in single cell multiomics assays and/or high-throughput sequencing. 
     There are provided, in some embodiments, primer panels designed to amplify nucleic acids encoding BCR/TCR immune receptor polypeptides. Amplification reactions performed using the methods and compositions disclosed herein can yield a set of complete/full variable domain of some or all immune receptor chain types, such as all BCR and TCR chain types found in human and/or mouse (for example IGH, IGL, IGK, TRA, TRB, TRD, TRG) from immune cell types. The nucleic acid template employed the disclosed amplification reactions can be generated by reverse transcription/extension of mRNA transcripts encoding some or all above mentioned immune receptor chain types, and can be derived from the product of genetic recombination of Variable, Junction and/or Diversity section of immune repertoire. Some of the primer panels provided herein are designed by a sophisticated bioinformatics pipeline to target the conserved segment at the start of the constant domain of different chain types, while at the same time presenting minimal interference to other nucleotide sequences in a single cell multiomics assay. 
     The disclosed methods and compositions can recover a more complete set of variable domain as compared to currently available methods. Some embodiments of the compositions and methods provided herein have optimal performance in a single cell multiomics assay and/or high-throughput sequencing. Additionally, the disclosed compositions and methods have been designed to present minimal interference to the accurate measurement of other features in a single cell multiomics assay. 
     Due to the mutation variants of constant domains in different mouse strains, recovery of a complete set of variable domain has been considered a challenging task and is an outstanding issue in the art. Compared to similar and currently available primer panels, the primer panels provided herein have been designed with the most updated knowledge collected in IMGT database which documented the variation of the constant domain from multiple mouse strains. By taking advantage of this information, the disclosed compositions (e.g., primer panels) are designed to target the highly conservative section shared by all known constant domain variants, and therefore these primer panels can recover the most complete set of variable domains, regardless of the variation in the constant domain sequence among strains of mouse. This more complete coverage can be essential for identifying the clonotypes of T- and B-cell receptors and revealing the complete breadth and depth of the immune repertoire, by single cell sequencing. 
     Another challenge in designing such primer panels in single cell multiomics assays lies in the possibility of nucleotide sequence interactions and undesired interference. The disclosed compositions (e.g., primers, primer panels) have been designed to overcome this issue. This was accomplished by developing and utilizing a sophisticated scoring system to measure tendency of sequence interaction, secondary structure, dimer formation at theoretical primer concentration and salt concentration, temperature and by employing physical-chemical and thermodynamics feature prediction of primer secondary structures. This scoring system can take into consideration the predicted interaction of nucleotide sequences within the hereby mentioned panel, between the hereby mentioned panel and other panels to be used in combination of multiple forms of single cell multiomics assay, other primer vs nucleotide sequence interaction including universal adapter sequence, sequencing primer binding site sequence, cell label sequence, and molecule barcode sequence. The scoring system can generate a score ranked list of primers that have minimal potential to yield above-mentioned unwanted interactions.  FIG.  8    depicts a non-limiting exemplary workflow for the generation of the primer panels disclosed herein. 
     There are provided, in some embodiments, a mixture or cocktail of nucleotide sequences to be used as primers for the amplification of any nucleic acid sequences derived from genetic materials of immune system, e.g., encoding BCR/TCR immune receptor polypeptides. Some embodiments of the methods and compositions provided herein comprise a microsurface prepared to contain primer sequences that are capable of binding nucleic acids derived from genetic materials of immune system, e.g., encoding BCR/TCR immune receptor polypeptides. 
     Nucleic acids encoding immune receptor polypeptides are amplified with primers containing a sample/cell/molecule-specific barcode in some embodiments of the methods and compositions provided herein. 
     In some embodiments of the methods and compositions provided herein, individual nucleotide sequences can be assembled to form the mixture of nucleotide sequences to be used as primer mixture or cocktail. There are also provided, in some embodiments, nucleotide sequence based probes that allow detection of BCR/TCR sequences derived from genetic materials of immune system. 
     The primers and primer panels provided herein can be generated by a sophisticated multi-step workflow. First, a consensus sequence can be generated by collecting relevant records from most updated IMGT database and these collections can be aligned by groups to obtain a consensus sequence to represent each C gene groups. Second, Primer3 can be employed to design a large number of primers against consensus reverse-complementary sequence of IMGT alleles for each C gene groups. Third, each potential primer can be aligned to human/mouse transcriptome and universal adapter sequences appended to cell labels and other relevant sequences to exclude; each potential primer can be checked for heterodimer formation with base panels including IR, OncoBC and TCell for human and IR mouse for mouse. Finally, a sophisticated bioinformatics pipeline can be employed to calculate an “Overall Score” for each potential primer and to place each potential primer in a consensus region bin and rank potential primers grouped by each consensus C gene group.  FIG.  8    depicts a non-limiting exemplary workflow for the generation of the primer panels disclosed herein. 
     In some embodiments, amplification reactions performed according to the disclosed methods (e.g., pretzel bead sequence extension, amplifying transcripts barcoded on the 3′ end and subsequently barcoded on the 5′ end following a template switching reaction and intermolecular and/or intramolecular hybridization and extension) using the primer sets provided herein can generate amplicons containing the full length of variable region, which can be of high interest to pharmaceuticals and biotech companies driven to discover and develop biologics therapies. In some embodiments of the disclosed methods and compositions, it is possible to recover the physical nucleotide sequence of the complete variable region, such as, for example, in single cell multiomics assays, which is not possible with currently available single cell sequencing assays. 
     Disclosed herein include methods for amplifying a plurality of nucleic acid molecules. The method can comprise: contacting a plurality of nucleic acid molecules comprising a first universal sequence with a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more of the compositions disclosed herein (e.g., one or more first amplification primers); and amplifying the plurality of nucleic acid molecules to generate a first plurality of amplified products. The method can comprise: amplifying the first plurality of amplified products using a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more of the compositions disclosed herein (e.g., one or more second amplification primers), thereby generating a second plurality of amplified products. In some embodiments, one or more nucleic acid molecules comprises the sequence of: a constant domain of an immunoglobulin heavy chain and/or a constant domain of an immunoglobulin light chain. In some embodiments, one or more nucleic acid molecules comprises the sequence of: a constant domain of a T Cell Receptor Alpha Chain, a constant domain of a T Cell Receptor Beta Chain, a constant domain of a T Cell Receptor Delta Chain, a constant domain of a T Cell Receptor Gamma Chain, or any combination thereof. The method can comprise obtaining the sequence information of the first plurality of amplified products, the second plurality of amplified products, or products thereof. The plurality of nucleic acid molecules can comprise deoxyribonucleic acid (DNA) molecules and/or ribonucleic acid (RNA) molecules. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 10-17; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 18-20. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. 
     Disclosed herein include compositions for the identification and quantification of a B Cell Receptor (BCR) repertoire in a sample. In some embodiments, the composition comprises: one or more first primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more first primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 10-17; one or more first primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more first primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 18-20; one or more second primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more second primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. 
     The immunoglobulin heavy chain can comprise an alpha chain, a delta chain, an epsilon chain, a gamma chain, a mu chain, or any combination thereof. The immunoglobulin light chain can comprise a kappa chain and/or a lambda chain. The constant domain of an immunoglobulin heavy chain can comprise Immunoglobulin Heavy Constant Alpha (IGHA), Immunoglobulin Heavy Constant Delta (IGHD), Immunoglobulin Heavy Constant Epsilon (IGHE), Immunoglobulin Heavy Constant Gamma (IGHG), Immunoglobulin Heavy Constant Mu (IGHM), or any combination thereof. The constant domain of an immunoglobulin heavy chain can comprise Immunoglobulin Heavy Constant Gamma 1 (IGHG1), Immunoglobulin Heavy Constant Gamma 2A (IGHG2A), Immunoglobulin Heavy Constant Gamma 2C (IGHG2C), Immunoglobulin Heavy Constant Gamma 2B (IGHG2B), Immunoglobulin Heavy Constant Gamma 3 (IGHG3), or any combination thereof. The constant domain of an immunoglobulin light chain can comprise Immunoglobulin Kappa Constant (IGKC), Immunoglobulin Lambda Constant (IGLC), or any combination thereof. The constant domain of an immunoglobulin light chain can comprise Immunoglobulin Lambda Constant 1 (IGLC1), Immunoglobulin Lambda Constant 2 (IGLC2), Immunoglobulin Lambda Constant 3 (IGLC3), or any combination thereof. The constant domain of an immunoglobulin heavy chain can comprise the constant domain of a mouse immunoglobulin heavy chain, and wherein the constant domain of an immunoglobulin light chain comprises the constant domain of a mouse immunoglobulin light chain. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 1; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 2; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 3; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 4. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. 
     Disclosed herein include compositions for the identification and quantification of a T Cell Receptor (TCR) repertoire in a sample. In some embodiments, the composition comprises: one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 1; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 2; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 3; one or more first primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more first primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 4; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more second primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more second primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. 
     The constant domain of the T Cell Receptor Gamma Chain can comprise T Cell Receptor Gamma Constant 1 (TRGC1), T Cell Receptor Gamma Constant 2 (TRGC2), T Cell Receptor Gamma Constant 4 (TRGC4), or any combination thereof. The constant domain of a T Cell Receptor Alpha Chain can comprise T Cell Receptor Alpha Constant (TRAC). The constant domain of a T Cell Receptor Beta Chain can comprise T Cell Receptor Beta Constant (TRBC). The constant domain of a T Cell Receptor Delta Chain can comprise T Cell Receptor Delta Constant (TRDC). The constant domain of a T Cell Receptor Alpha Chain can comprise the constant domain of a mouse T Cell Receptor Alpha Chain, wherein the constant domain of a T Cell Receptor Beta Chain comprises the constant domain of a mouse T Cell Receptor Beta Chain, wherein the constant domain of a T Cell Receptor Gamma Chain can comprise the constant domain of a mouse T Cell Receptor Gamma Chain, and wherein the constant domain of a T Cell Receptor Delta Chain comprises the constant domain of a mouse T Cell Receptor Delta Chain. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of an immunoglobulin heavy chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. Said probe or primer can comprise a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 10-17, 21-28, and 37-44. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of an immunoglobulin light chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. Said probe or primer can comprise a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 18-20, 29-31, and 45-47. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. Said probe or primer can comprise a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 1, 5, and 32. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. Said probe or primer can comprise a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 2, 6, and 33. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. Said probe or primer can comprise a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 3, 7, and 34. 
     Disclosed herein include probes or primers up to about 100 nucleotides in length which is capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain. In some embodiments, the probe or primer comprises: a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36, or sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. Said probe or primer can comprise a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. Said probe or primer can consist of a sequence selected from the group consisting of SEQ ID NOs: 4, 8-9, and 35-36. 
     In some embodiments of the method and compositions provided herein, SEQ ID NO: 4 is replaced with CATCCTTTTCTTTCCAATACACCC (SEQ ID NO: 48). In some embodiments of the method and compositions provided herein, SEQ ID NO: 9 is replaced with CAGACGTGTGCTCTTCCGATCTAATAGTAGGCTTGGGAGAAAAGTCTG (SEQ ID NO: 49). In some embodiments of the method and compositions provided herein, SEQ ID NO: 36 is replaced with AATAGTAGGCTTGGGAGAAAAGTCTG (SEQ ID NO: 50). Examples of oligonucleotides capable of specifically hybridizing to the constant region of an immune receptor (e.g., TCR, BCR) include, but are not limited, SEQ ID NOs: 1-47 as provided in Tables 1-6 and sequences that exhibits at least about 85% identity to any one of SEQ ID NOs: 1-47. Also provided herein are oligonucleotides (for example amplification primers or probes) containing 1, 2, 3, 4 or more mismatches or universal nucleotides relative to SEQ ID NOs: 1-50 or the complement thereof, including oligonucleotides that are at least 80% identical (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) to SEQ ID NOs: 1-50 or the complement thereof. In some embodiments, the oligonucleotide comprises a sequence selected from SEQ ID NO: 1-50. In some embodiments, the oligonucleotide comprises a sequence that is at least about 85% identical to a sequence selected from SEQ ID NO: 1-50. In some embodiments, the oligonucleotide consists of a sequence selected from SEQ ID NO: 1-50. In some embodiments, the oligonucleotide consists of a sequence that is at least about 85% identical or at least about 95% identical to a sequence selected from SEQ ID NO: 1-50. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 TCR (N1) Primers 
               
            
           
           
               
               
               
            
               
                   
                 Primer Name 
                 Primer Sequence (5′-3′) 
               
               
                   
                   
               
               
                   
                 TRAC_N1 
                 TTTTCGGCACATTGATTTGGGAG 
               
               
                   
                   
                 (SEQ ID NO: 1) 
               
               
                   
                   
               
               
                   
                 TRBC_N1 
                 CTCAGGCAGTAGCTATAATTGCT 
               
               
                   
                   
                 (SEQ ID NO: 2) 
               
               
                   
                   
               
               
                   
                 TRDC_N1 
                 CAATCTTCTTGGATGATCTGAGACT 
               
               
                   
                   
                 (SEQ ID NO: 3) 
               
               
                   
                   
               
               
                   
                 TRGC1-TRGC2- 
                 GGAAAGAACTTTTCAAGGAGACAAAGG 
               
               
                   
                 TRGC4_N1 
                 (SEQ ID NO: 4) 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 TCR (N2) Primers 
               
            
           
           
               
               
            
               
                   
                 Primer Sequence (5′-3′) 
               
               
                   
                 *partial Illumina 
               
               
                 Primer Name 
                 P7 adaptor sequence underlined 
               
               
                   
               
               
                 TRAC_N2 
                   CAGACGTGTGCTCTTCCGATCT AGGTTCTGGGTTCTG 
               
               
                   
                 GATGT (SEQ ID NO: 5) 
               
               
                   
               
               
                 TRBC_N2 
                   CAGACGTGTGCTCTTCCGATCT CAATCTCTGCTTTTG 
               
               
                   
                 ATGGCTC (SEQ ID NO: 6) 
               
               
                   
               
               
                 TRDC_N2 
                   CAGACGTGTGCTCTTCCGATCT GTAGAAATCTTTCAC 
               
               
                   
                 CAGACAAGC (SEQ ID NO: 7) 
               
               
                   
               
               
                 TRGC1- 
                   CAGACGTGTGCTCTTCCGATCT TTGGGGGAAATGTCT 
               
               
                 TRGC2_N2 
                 GCA (SEQ ID NO: 8) 
               
               
                   
               
               
                 TRGC4_N2 
                   CAGACGTGTGCTCTTCCGATCT ATAGTAGGCTTGGGA 
               
               
                   
                 GAAAAGTCTGA (SEQ ID NO: 9) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 BCR (N1) Primers 
               
            
           
           
               
               
            
               
                 Primer Name 
                 Primer Sequence (5′-3′) 
               
               
                   
               
               
                 IGHA_N1 
                 AACTGGCTGCTCATGGTGTA (SEQ ID NO: 10) 
               
               
                   
               
               
                 IGHD_N1 
                 AAGTGTGGTTGAGGTTCAGTTCTG (SEQ ID NO: 11) 
               
               
                   
               
               
                 IGRE_N1 
                 GAAGTTCACAGTGCTCATGTTC (SEQ ID NO: 12) 
               
               
                   
               
               
                 IGHG1 N1 
                 CAGAGTGTAGAGGTCAGACT (SEQ ID NO: 13) 
               
               
                   
               
               
                 IGHG2A- 
                 TCGAGGTTACAGTCACTGAG (SEQ ID NO: 14) 
               
               
                 IGHG2C_N1 
                   
               
               
                   
               
               
                 IGHG2B_N1 
                 GATCCAGAGTTCCAAGTCACAG (SEQ ID NO: 15) 
               
               
                   
               
               
                 IGHG3_N1 
                 TACGTTGCAGATGACAGTCT (SEQ ID NO: 16) 
               
               
                   
               
               
                 IGHM_N1 
                 TGGATGACTTCAGTGTTGTTCTG (SEQ ID NO: 17) 
               
               
                   
               
               
                 IGKC_N1 
                 TGTAGGTGCTGTCTTTGCTG (SEQ ID NO: 18) 
               
               
                   
               
               
                 IGLC1_N1 
                 CTGTAACTGCTATGCCTTTCCC (SEQ ID NO: 19) 
               
               
                   
               
               
                 IGLC2- 
                 TTGGTGGGATTTGAAGTGTCC (SEQ ID NO: 20) 
               
               
                 IGLC3_N1 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 BCR (N2) Primers 
               
            
           
           
               
               
            
               
                 Primer 
                 Primer Sequence (5′-3′) *partial 
               
               
                 Name 
                 Illumina P7 adaptor sequence underlined 
               
               
                   
               
               
                 IGHA_N2 
                   CAGACGTGTGCTCTTCCGATCT TGTCAGTGGGTAGATGGT 
               
               
                   
                 GG (SEQ ID NO: 21) 
               
               
                   
               
               
                 IGHD_N2 
                   CAGACGTGTGCTCTTCCGATCT CTGACTTCCAATTACTAA 
               
               
                   
                 ACAGCC (SEQ ID NO: 22) 
               
               
                   
               
               
                 IGRE_N2 
                   CAGACGTGTGCTCTTCCGATCT TAGAGCTGAGGGTTCCTG 
               
               
                   
                 ATAG (SEQ ID NO: 23) 
               
               
                   
               
               
                 IGHG1_N2 
                   CAGACGTGTGCTCTTCCGATCT CAGTGGATAGACAGATGG 
               
               
                   
                 GGGT (SEQ ID NO: 24) 
               
               
                   
               
               
                 IGHG2A- 
                   CAGACGTGTGCTCTTCCGATCT ATGGGGCTGTTGTTTTGG 
               
               
                 IGHG2C_N2 
                 (SEQ ID NO: 25) 
               
               
                   
               
               
                 IGHG2B-N2 
                   CAGACGTGTGCTCTTCCGATCT GTGGATAGACTGATGGGG 
               
               
                   
                 GTGTT (SEQ ID NO: 26) 
               
               
                   
               
               
                 IGHG3_N2 
                   CAGACGTGTGCTCTTCCGATCT AGGGAAGTAGCCTTTGAC 
               
               
                   
                 AAG (SEQ ID NO: 27) 
               
               
                   
               
               
                 IGHM_N2 
                   CAGACGTGTGCTCTTCCGATC TGACATTTGGGAAGGACTG 
               
               
                   
                 ACTC (SEQ ID NO: 28) 
               
               
                   
               
               
                 IGKC_N2 
                   CAGACGTGTGCTCTTCCGATCT AGATGTTAACTGCTCACT 
               
               
                   
                 GGATG (SEQ ID NO: 29) 
               
               
                   
               
               
                 IGLC1_N2 
                   CAGACGTGTGCTCTTCCGATCT GTTAGTCTCGAGCTCTTC 
               
               
                   
                 AGA (SEQ ID NO: 30) 
               
               
                   
               
               
                 IGLC2- 
                   CAGACGTGTGCTCTTCCGATCT CAGTGTGGCTTTGTTTTC 
               
               
                 IGLC3_N2 
                 CT (SEQ ID NO: 31) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 TCR (N2-NA) Primers 
               
            
           
           
               
               
               
            
               
                   
                 Primer Name 
                 Primer Sequence (5′-3′) 
               
               
                   
                   
               
               
                   
                 TRAC_N2-NA 
                 AGGTTCTGGGTTCTGGATGT 
               
               
                   
                   
                 (SEQ ID NO: 32) 
               
               
                   
                   
               
               
                   
                 TRBC_N2-NA 
                 CAATCTCTGCTTTTGATGGCTC 
               
               
                   
                   
                 (SEQ ID NO: 33) 
               
               
                   
                   
               
               
                   
                 TRDC_N2-NA 
                 GTAGAAATCTTTCACCAGACAAGC 
               
               
                   
                   
                 (SEQ ID NO: 34) 
               
               
                   
                   
               
               
                   
                 TRGC1- 
                 TTGGGGGAAATGTCTGCA 
               
               
                   
                 TRGC2_N2-NA 
                 (SEQ ID NO: 35) 
               
               
                   
                   
               
               
                   
                 TRGC4_N2-NA 
                 ATAGTAGGCTTGGGAGAAAAGTCTGA 
               
               
                   
                   
                 (SEQ ID NO: 36) 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 BCR (N2-NA) Primers 
               
            
           
           
               
               
            
               
                 Primer Name 
                 Primer Sequence (5′-3′) 
               
               
                   
               
               
                 IGHA_N2-NA 
                 TGTCAGTGGGTAGATGGTGG (SEQ ID NO: 37) 
               
               
                   
               
               
                 IGHD_N2-NA 
                 CTGACTTCCAATTACTAAACAGCC 
               
               
                   
                 (SEQ ID NO: 38) 
               
               
                   
               
               
                 IGRE_N2-NA 
                 TAGAGCTGAGGGTTCCTGATAG (SEQ ID NO: 39) 
               
               
                   
               
               
                 IGHG1_N2-NA 
                 CAGTGGATAGACAGATGGGGGT (SEQ ID NO: 40) 
               
               
                   
               
               
                 IGHG2A- 
                 ATGGGGCTGTTGTTTTGG (SEQ ID NO: 41) 
               
               
                 IGHG2C_N2-NA 
                   
               
               
                   
               
               
                 IGHG2B_N2-NA 
                 GTGGATAGACTGATGGGGGTGTT (SEQ ID NO: 42) 
               
               
                   
               
               
                 IGHG3_N2-NA 
                 AGGGAAGTAGCCTTTGACAAG (SEQ ID NO: 43) 
               
               
                   
               
               
                 IGHM_N2-NA 
                 GACATTTGGGAAGGACTGACTC (SEQ ID NO: 44) 
               
               
                   
               
               
                 IGKC_N2-NA 
                 AGATGTTAACTGCTCACTGGATG (SEQ ID NO: 45) 
               
               
                   
               
               
                 IGLC1_N2-NA 
                 GTTAGTCTCGAGCTCTTCAGA (SEQ ID NO: 46) 
               
               
                   
               
               
                 IGLC2- 
                 CAGTGTGGCTTTGTTTTCCT (SEQ ID NO: 47) 
               
               
                 IGLC3_N2-NA 
               
               
                   
               
            
           
         
       
     
     Labeled Oligonucleotide Probes 
     There are provided, in some embodiments, reporter (affinity, fluorophore) tagged nucleic acid probes for the detection of nucleic acids derived from genetic materials of immune system, e.g., encoding BCR and/or TCR immune receptor polypeptides. As used herein, a “probe” can refer to an polynucleotide that can hybridizes (e.g., specifically) to a target sequence in a nucleic acid, under conditions that allow hybridization, thereby allowing detection of the target sequence or amplified nucleic acid. A probe&#39;s “target” generally refers to a sequence within or a subset of an amplified nucleic acid sequence which hybridizes specifically to at least a portion of a probe oligomer by standard hydrogen bonding (i.e., base pairing). A probe may comprise target-specific sequences and other sequences that contribute to three-dimensional conformation of the probe. Sequences are “sufficiently complementary” if they allow stable hybridization in appropriate hybridization conditions of a probe oligomer to a target sequence that is not completely complementary to the probe&#39;s target-specific sequence. The length of a probe can vary, for example, from about 5 to about 100 nucleotides, from about 10 to about 50 nucleotides, from about 15 to about 40 nucleotides, or from about 20 to about 30 nucleotides. The length of a probe can be about 10 nucleotides, about 20 nucleotides, about 25 nucleotides, about 30 nucleotides, about 35 nucleotides, about 40 nucleotides, about 50 nucleotides, about 100 nucleotides, or a range between any two of these values. In some embodiments, the probe has a length of 10 to about 50 nucleotides. For example, the primers and or probes can be at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, or more nucleotides. In some embodiments, the probe can be non-sequence specific. 
     Oligonucleotide probes can, in some embodiments, include a detectable moiety. For example, the oligonucleotide probes disclosed herein can comprise a radioactive label. Non-limiting examples of radioactive labels include  3 H,  14 C,  32 P, and  35 S. In some embodiments, oligonucleotide probes can include one or more non-radioactive detectable markers or moieties, including but not limited to ligands, fluorophores, chemiluminescent agents, enzymes, and antibodies. Other detectable markers for use with probes, which can enable an increase in sensitivity of the method of the invention, include biotin and radio-nucleotides. It will become evident to the person of ordinary skill that the choice of a particular label dictates the manner in which it is bound to the probe. For example, oligonucleotide probes labeled with one or more dyes, such that upon hybridization to a template nucleic acid, a detectable change in fluorescence is generated. While non-specific dyes may be desirable for some applications, sequence-specific probes can provide more accurate measurements of amplification. One configuration of sequence-specific probe can include one end of the probe tethered to a fluorophore, and the other end of the probe tethered to a quencher. When the probe is unhybridized, it can maintain a stem-loop configuration, in which the fluorophore is quenched by the quencher, thus preventing the fluorophore from fluorescing. When the probe is hybridized to a template nucleic sequence, it is linearized, distancing the fluorophore from the quencher, and thus permitting the fluorophore to fluoresce. Another configuration of sequence-specific probe can include a first probe tethered to a first fluorophore of a FRET pair, and a second probe tethered to a second fluorophore of a FRET pair. The first probe and second probe can be configured to hybridize to sequences of an amplicon that are within sufficient proximity to permit energy transfer by FRET when the first probe and second probe are hybridized to the same amplicon. 
     In some embodiments the probe is a TaqMan probe. TaqMan probes can comprise a fluorophore and a quencher. The quencher molecule can quench the fluorescence emitted by the fluorophore when excited by the cycler&#39;s light source via Förster resonance energy transfer (FRET). As long as the fluorophore and the quencher are in proximity, quenching can inhibit any detectable (e.g., fluorescence) signals. TaqMan probes provided herein can designed such that they anneal within a DNA region amplified by primers provided herein. Without being bound by any particular theory, in some embodiments, as a PCR polymerase (e.g., Taq) extends the primer and synthesizes a nascent strand on a single-strand template, the 5′ to 3′ exonuclease activity of the PCR polymerase degrades the probe that has annealed to the template. Degradation of the probe can release the fluorophore from it and break the proximity to the quencher, thereby relieving the quenching effect and allowing fluorescence of the fluorophore. Hence, fluorescence detected in the quantitative PCR thermal cycler can, in some embodiments, be directly proportional to the fluorophore released and the amount of DNA template present in the PCR. 
     In some embodiments, the sequence specific probe comprises an oligonucleotide as disclosed herein conjugated to a fluorophore. In some embodiments, the probe is conjugated to two or more fluorophores. Examples of fluorophores include: xanthene dyes, e.g., fluorescein and rhodamine dyes, such as fluorescein isothiocyanate (FITC), 2-[ethylamino)-3-(ethylimino)-2-7-dimethyl-3H-xanthen-9-yl]benzoic acid ethyl ester monohydrochloride (R6G)(emits a response radiation in the wavelength that ranges from about 500 to 560 nm), 1,1,3,3,3′,3′-Hexamethylindodicarbocyanine iodide (HIDC) (emits a response radiation in the wavelength that ranged from about 600 to 660 nm), 6-carboxyfluorescein (commonly known by the abbreviations FAM and F), 6-carboxy-2′,4′,7′,4,7-hexachlorofluorescein (HEX), 6-carboxy-4′,5′-dichloro-2′,7′-dimethoxyfluorescein (JOE or J), N,N,N′,N′-tetramethyl-6-carboxyrhodamine (TAMRA or T), 6-carboxy-X-rhodamine (ROX or R), 5-carboxyrhodamine-6G (R6G5 or G5), 6-carboxyrhodamine-6G (R6G6 or G6), and rhodamine 110; cyanine dyes, e.g. Cy3, Cy5 and Cy7 dyes; coumarins, e.g., umbelliferone; benzimide dyes, e.g. Hoechst 33258; phenanthridine dyes, e.g. Texas Red; ethidium dyes; acridine dyes; carbazole dyes; phenoxazine dyes; porphyrin dyes; polymethine dyes, e.g. cyanine dyes such as Cy3 (emits a response radiation in the wavelength that ranges from about 540 to 580 nm), Cy5 (emits a response radiation in the wavelength that ranges from about 640 to 680 nm), etc; BODIPY dyes and quinoline dyes. Specific fluorophores of interest include: Pyrene, Coumarin, Diethylaminocoumarin, FAM, Fluorescein Chlorotriazinyl, Fluorescein, R110, Eosin, JOE, R6G, HIDC, Tetramethylrhodamine, TAMRA, Lissamine, ROX, Napthofluorescein, Texas Red, Napthofluorescein, Cy3, and Cy5, CAL fluor orange, and the like. 
     In some embodiments, the probe is conjugated to a quencher. A quencher can absorb electromagnetic radiation and dissipate it as heat, thus remaining dark. Example quenchers include Dabcyl, NFQ&#39;s, such as BHQ-1 or BHQ-2 (Biosearch), IOWA BLACK FQ (IDT), and IOWA BLACK RQ (IDT). In some embodiments, the quencher is selected to pair with a fluorphore so as to absorb electromagnetic radiation emitted by the fluorophore. Flourophore/quencher pairs useful in the compositions and methods disclosed herein are well-known in the art, and can be found, e.g., described in Marras, “Selection of Fluorophore and Quencher Pairs for Fluorescent Nucleic Acid Hybridization Probes” available at www.molecular-beacons.org/download/marras,mmb06%28335%293.pdf. Examples of quencher moieties include, but are not limited to: a dark quencher, a Black Hole Quencher® (BHQ®) (e.g., BHQ-0, BHQ-1, BHQ-2, BHQ-3), a Qxl quencher, an ATTO quencher (e.g., ATTO 540Q, ATTO 580Q, and ATTO 612Q), dimethylaminoazobenzenesulfonic acid (Dabsyl), Iowa Black RQ, Iowa Black FQ, IRDye QC-1, a QSY dye (e.g., QSY 7, QSY 9, QSY 21), AbsoluteQuencher, Eclipse, and metal clusters such as gold nanoparticles, and the like. Examples of an ATTO quencher include, but are not limited to: ATTO 540Q, ATTO 580Q, and ATTO 612Q. Examples of a Black Hole Quencher® (BHQ®) include, but are not limited to: BHQ-0 (493 nm), BHQ-1 (534 nm), BHQ-2 (579 nm) and BHQ-3 (672 nm). 
     In some embodiments, a detectable label is a fluorescent label selected from: an Alexa Fluor® dye (e.g., Alexa Fluor® 350, Alexa Fluor® 405, Alexa Fluor® 430, Alexa Fluor® 488, Alexa Fluor® 500, Alexa Fluor® 514, Alexa Fluor® 532, Alexa Fluor® 546, Alexa Fluor® 555, Alexa Fluor® 568, Alexa Fluor® 594, Alexa Fluor® 610, Alexa Fluor® 633, Alexa Fluor® 635, Alexa Fluor® 647, Alexa Fluor® 660, Alexa Fluor® 680, Alexa Fluor® 700, Alexa Fluor® 750, Alexa Fluor® 790), an ATTO dye (e.g., ATTO 390, ATTO 425, ATTO 465, ATTO 488, ATTO 495, ATTO 514, ATTO 520, ATTO 532, ATTO Rho6G, ATTO 542, ATTO 550, ATTO 565, ATTO Rho3B, ATTO Rhol 1, ATTO Rhol2, ATTO Thiol 2, ATTO RholOl, ATTO 590, ATTO 594, ATTO Rhol3, ATTO 610, ATTO 620, ATTO Rhol4, ATTO 633, ATTO 647, ATTO 647N, ATTO 655, ATTO Oxal2, ATTO 665, ATTO 680, ATTO 700, ATTO 725, ATTO 740), a DyFight dye, a cyanine dye (e.g., Cy2, Cy3, Cy3.5, Cy3b, Cy5, Cy5.5, Cy7, Cy7.5), a FluoProbes dye, a Sulfo Cy dye, a Seta dye, an IRIS Dye, a SeTau dye, an SRfluor dye, a Square dye, fluorescein (FITC), tetramethylrhodamine (TRITC), Texas Red, Oregon Green, Pacific Blue, Pacific Green, Pacific Orange, a quantum dot, and a tethered fluorescent protein. 
     In some embodiments, a fluorophore is attached to a first end of the probe, and a quencher is attached to a second end of the probe. Attachment can include covalent bonding, and can optionally include at least one linker molecule positioned between the probe and the fluorophore or quencher. In some embodiments, a fluorophore is attached to a 5′ end of a probe, and a quencher is attached to a 3′ end of a probe. In some embodiments, a fluorophore is attached to a 3′ end of a probe, and a quencher is attached to a 5′ end of a probe. Examples of probes that can be used in quantitative nucleic acid amplification include molecular beacons, SCORPION™ probes (Sigma), TAQMAN™ probes (Life Technologies) and the like. Other nucleic acid detection technologies that are useful in the embodiments disclosed herein include, but are not limited to nanoparticle probe technology (See, Elghanian, et al. (1997)  Science  277:1078-1081.) and Amplifluor probe technology (See, U.S. Pat. Nos. 5,866,366; 6,090,592; 6,117,635; and 6,117,986). 
     As used herein, nucleic acid amplification can refer to any known procedure for obtaining multiple copies of a target nucleic acid sequence or its complement or fragments thereof, using sequence-specific methods. Examples of known amplification methods include, but are not limited to, polymerase chain reaction (PCR), ligase chain reaction (LCR), loop-mediated isothermal amplification (LAMP), strand displacement amplification (SDA) (e.g., multiple displacement amplification (MDA)), replicase-mediated amplification, immuno-amplification, nucleic acid sequence based amplification (NASBA), self-sustained sequence replication (3SR), rolling circle amplification, and transcription-mediated amplification (TMA). A wide variety of PCR methods have been described in many sources, for example, Ausubel et al. (eds.), Current Protocols in Molecular Biology, Section 15, John Wiley &amp; Sons, Inc., New York (1994). Examples of PCR method include, but not limited to, Real-Time PCR, End-Point PCR, Amplified fragment length polymorphism PCR (AFLP-PCR), Alu-PCR, Asymmetric PCR, Colony PCR, DD-PCR, Degenerate PCR, Hot-start PCR, In situ PCR, Inverse PCR Long-PCR, Multiplex PCR, Nested PCR, PCR-ELISA, PCR-RFLP, PCR-single strand conformation polymorphism (PCR-SSCP), quantitative competitive PCR (QC-PCR), rapid amplification of cDNA ends-PCR (RACE-PCR), Random Amplification of Polymorphic DNA-PCR (RAPD-PCR), Real-Time PCR, Repetitive extragenic palindromic-PCR (Rep-PCR), reverse transcriptase PCR (RT-PCR), TAIL-PCR, Touchdown PCR and Vectorette PCR. 
     Real-time PCR, also called quantitative real time polymerase chain reaction (QRT-PCR), can be used to simultaneously quantify and amplify a specific part of a given nucleic acid molecule. It can be used to determine whether a specific sequence is present in the sample; and if it is present, the number of copies of the sequence that are present. The term “real-time” can refer to periodic monitoring during PCR. Certain systems such as the ABI 7700 and 7900HT Sequence Detection Systems (Applied Biosystems, Foster City, Calif.) conduct monitoring during each thermal cycle at a pre-determined or user-defined point. Real-time analysis of PCR with fluorescence resonance energy transfer (FRET) probes measures fluorescent dye signal changes from cycle-to-cycle, preferably minus any internal control signals. The real-time procedure follows the general pattern of PCR, but the nucleic acid is quantified after each round of amplification. Two examples of method of quantification are the use of fluorescent dyes (e.g., SYBRGreen) that intercalate into double-stranded DNA, and modified DNA oligonucleotide probes that fluoresce when hybridized with a complementary DNA. Intercalating agents have a relatively low fluorescence when unbound, and a relatively high fluorescence upon binding to double-stranded nucleic acids. As such, intercalating agents can be used to monitor the accumulation of double strained nucleic acids during a nucleic acid amplification reaction. Examples of such non-specific dyes useful in the embodiments disclosed herein include intercalating agents such as SYBR Green I (Molecular Probes), propidium iodide, ethidium bromide, and the like. 
     The oligonucleotide probe can be, for example, between about 10 and about 45 nucleotides in length, and comprises a detectable moiety (e.g., a signal moiety, a detectable label). In some embodiments, the contacting is performed under conditions allowing for the specific hybridization of the primers to the corresponding targeted gene region if the target organism is present in the sample. The presence and/or amount of probe that is specifically bound to the corresponding targeted gene region (if present in the sample being tested) can be determined, wherein bound probe is indicative of the presence of the corresponding target organism in the sample. In some embodiments, the amount of bound probe is used to determine the amount of the corresponding target organism in the sample. 
     There are provided, in some embodiments, methods of determining the presence, identity, and/or amount (e.g., counting) of a target nucleic acid (e.g., an immune receptor) in a sample. The determining step can be achieved using any methods known to those skilled in the art, including but not limited to, in situ hybridization, following the contacting step. The detection of hybrid duplexes (i.e., of a probe specifically bound to the targeted gene region) can be carried out by a number of methods. Typically, hybridization duplexes are separated from unhybridized nucleic acids and the labels bound to the duplexes are then detected. Such labels refer to radioactive, fluorescent, biological or enzymatic tags or labels of standard use in the art. A label can be conjugated to either the oligonucleotide probes or the nucleic acids derived from the biological sample. Those of skill in the art will appreciate that wash steps may be employed to wash away excess sample/target nucleic acids or oligonucleotide probe (as well as unbound conjugate, where applicable). Further, standard heterogeneous assay formats are suitable for detecting the hybrids using the labels present on the oligonucleotide primers and probes. Determining the presence or amount of one or more amplicons can comprise contacting said amplicons with a plurality of oligonucleotide probes. At least one of the plurality of oligonucleotide probes comprises a fluorescence emitter moiety and a fluorescence quencher moiety. In some embodiments, determining the presence or amount of one or more amplicons comprises measuring a detectable signal, such as, for example, a detectable signal from a probe. 
     In some embodiments, determining the presence or amount of one or more amplicons comprises measuring a detectable signal, such as, for example, a detectable signal from a probe (e.g., after cleavage of the probe by the 5′-3′ exonuclease activity of a PCR polymerase (e.g., Taq)). Determining the presence or amount of one or more amplicons can comprise measuring a detectable signal, such as, for example, a detectable signal from a probe. The measuring can in some embodiments be quantitative, e.g., in the sense that the amount of signal detected can be used to determine the amount of target nucleic acid (e.g., an immune receptor) present in the sample. The measuring can in some embodiments be qualitative, e.g., in the sense that the presence or absence of detectable signal can indicate the presence or absence of targeted DNA (e.g., virus, SNP, etc.). In some embodiments, a detectable signal will not be present (e.g., above a given threshold level) unless the targeted DNA(s) (e.g., virus, SNP, etc.) is present above a particular threshold concentration. In some embodiments, a disclosed method can be used to determine the amount of a target nucleic acid (e.g., an immune receptor) in a sample (e.g., a sample comprising the target nucleic acid and a plurality of non-target nucleic acids). Determining the amount of a target nucleic acid in a sample can comprise comparing the amount of detectable signal generated from a test sample to the amount of detectable signal generated from a reference sample. Determining the amount of a target nucleic acid in a sample can comprise: measuring the detectable signal to generate a test measurement; measuring a detectable signal produced by a reference sample to generate a reference measurement; and comparing the test measurement to the reference measurement to determine an amount of target nucleic acid present in the sample. Determining the amount of a target nucleic acid in a sample can be used to derive the presence and/or amount of an organism comprising said target nucleic acid in a sample. 
     In some embodiments, a detectable signal is measured is produced by the fluorescence-emitting dye pair of a probe. For example, in some embodiments, a disclosed method includes contacting amplicons with a probe comprising a fluorescence resonance energy transfer (FRET) pair or a quencher/fluor pair, or both. In some embodiments, a disclosed method includes contacting amplicons with a probe comprising a FRET pair. In some embodiments, a disclosed method includes contacting amplicons with a probe comprising a fluor/quencher pair. 
     Fluorescence-emitting dye pairs comprise a FRET pair or a quencher/fluor pair. In both embodiments of a FRET pair and a quencher/fluor pair, the emission spectrum of one of the dyes overlaps a region of the absorption spectrum of the other dye in the pair. As used herein, the term “fluorescence-emitting dye pair” is a generic term used to encompass both a “fluorescence resonance energy transfer (FRET) pair” and a “quencher/fluor pair,” both of which terms are discussed in more detail below. The term “fluorescence-emitting dye pair” is used interchangeably with the phrase “a FRET pair and/or a quencher/fluor pair.” 
     In some embodiments (e.g., when the probe includes a FRET pair) the probe produces an amount of detectable signal prior to being cleaved, and the amount of detectable signal that is measured is reduced when the probe is cleaved. In some embodiments, the probe produces a first detectable signal prior to being cleaved (e.g., from a FRET pair) and a second detectable signal when the probe is cleaved (e.g., from a quencher/fluor pair). As such, in some embodiments, the probe comprises a FRET pair and a quencher/fluor pair. 
     In some embodiments, the probe comprises a FRET pair. FRET is a process by which radiationless transfer of energy occurs from an excited state fluorophore to a second chromophore in close proximity. The range over which the energy transfer can take place is limited to approximately 10 nanometers (100 angstroms), and the efficiency of transfer is extremely sensitive to the separation distance between fluorophores. Thus, as used herein, the term “FRET” (“fluorescence resonance energy transfer”; also known as “Forster resonance energy transfer”) can refer to a physical phenomenon involving a donor fluorophore and a matching acceptor fluorophore selected so that the emission spectrum of the donor overlaps the excitation spectrum of the acceptor, and further selected so that when donor and acceptor are in close proximity (usually 10 nm or less) to one another, excitation of the donor will cause excitation of and emission from the acceptor, as some of the energy passes from donor to acceptor via a quantum coupling effect. Thus, a FRET signal serves as a proximity gauge of the donor and acceptor; only when they are in close proximity to one another is a signal generated. The FRET donor moiety (e.g., donor fluorophore) and FRET acceptor moiety (e.g., acceptor fluorophore) are collectively referred to herein as a “FRET pair”. 
     The donor-acceptor pair (a FRET donor moiety and a FRET acceptor moiety) is referred to herein as a “FRET pair” or a “signal FRET pair.” Thus, in some embodiments, a probe includes two signal partners (a signal pair), when one signal partner is a FRET donor moiety and the other signal partner is a FRET acceptor moiety. A probe that includes such a FRET pair (a FRET donor moiety and a FRET acceptor moiety) will thus exhibit a detectable signal (a FRET signal) when the signal partners are in close proximity (e.g., while on the same RNA molecule), but the signal will be reduced (or absent) when the partners are separated (e.g., after cleavage of the probe by the 5′-3′ exonuclease activity of a PCR polymerase (e.g., Taq)). FRET donor and acceptor moieties (FRET pairs) will be known to one of ordinary skill in the art and any convenient FRET pair (e.g., any convenient donor and acceptor moiety pair) can be used. 
     In some embodiments, one signal partner of a signal quenching pair produces a detectable signal and the other signal partner is a quencher moiety that quenches the detectable signal of the first signal partner (e.g., the quencher moiety quenches the signal of the signal moiety such that the signal from the signal moiety is reduced (quenched) when the signal partners are in proximity to one another, e.g., when the signal partners of the signal pair are in close proximity). 
     For example, in some embodiments, an amount of detectable signal increases when the probe is cleaved. For example, in some embodiments, the signal exhibited by one signal partner (a signal moiety, a fluorescence emitter moiety) is quenched by the other signal partner (a quencher signal moiety, a fluorescence quencher moiety), e.g., when both are present on the same ssDNA molecule prior to cleavage by the 5′-3′ exonuclease activity of a PCR polymerase (e.g., Taq). Such a signal pair is referred to herein as a “quencher/fluor pair”, “quenching pair”, or “signal quenching pair.” For example, in some embodiments, one signal partner (e.g., the first signal partner) is a signal moiety that produces a detectable signal that is quenched by the second signal partner (e.g., a quencher moiety). The signal partners of such a quencher/fluor pair will thus produce a detectable signal when the partners are separated (e.g., after cleavage of the probe by the 5′-3′ exonuclease activity of a PCR polymerase (e.g., Taq)), but the signal will be quenched when the partners are in close proximity (e.g., prior to cleavage of the probe by the 5′-3′ exonuclease activity of a PCR polymerase (e.g., Taq)). 
     A quencher moiety can quench a signal from the signal moiety (e.g., prior to cleavage of the probe by the 5′-3′ exonuclease activity of a PCR polymerase (e.g., Taq)) to various degrees. In some embodiments, a quencher moiety quenches the signal from the signal moiety where the signal detected in the presence of the quencher moiety (when the signal partners are in proximity to one another) is 95% or less of the signal detected in the absence of the quencher moiety (when the signal partners are separated). For example, in some embodiments, the signal detected in the presence of the quencher moiety can be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 15% or less, 10% or less, or 5% or less of the signal detected in the absence of the quencher moiety. In some embodiments, no signal (e.g., above background) is detected in the presence of the quencher moiety. 
     In some embodiments, the signal detected in the absence of the quencher moiety (when the signal partners are separated) is at least 1.2 fold greater (e.g., at least 1.3fold, at least 1.5 fold, at least 1.7 fold, at least 2 fold, at least 2.5 fold, at least 3 fold, at least 3.5 fold, at least 4 fold, at least 5 fold, at least 7 fold, at least 10 fold, at least 20 fold, or at least 50 fold greater, or a number or a range between any two of these values) than the signal detected in the presence of the quencher moiety (when the signal partners are in proximity to one another). 
     In some embodiments, the signal moiety is a fluorescent label. In some such embodiments, the quencher moiety quenches the signal (e.g., the light signal) from the fluorescent label (e.g., by absorbing energy in the emission spectra of the label). Thus, when the quencher moiety is not in proximity with the signal moiety, the emission (the signal) from the fluorescent label can be detectable because the signal is not absorbed by the quencher moiety. Any convenient donor acceptor pair (signal moiety/quencher moiety pair) can be used and many suitable pairs are known in the art. 
     In some embodiments, the quencher moiety absorbs energy from the signal moiety (also referred to herein as a “detectable label” or a “detectable moiety”) and then emits a signal (e.g., light at a different wavelength). Thus, in some embodiments, the quencher moiety is itself a signal moiety (e.g., a signal moiety can be 6- carboxyfluorescein while the quencher moiety can be 6-carboxy-tetramethylrhodamine), and in some such embodiments, the pair could also be a FRET pair. In some embodiments, a quencher moiety is a dark quencher. A dark quencher can absorb excitation energy and dissipate the energy in a different way (e.g., as heat). Thus, a dark quencher has minimal to no fluorescence of its own (does not emit fluorescence). 
     In some embodiments, cleavage of a probe can be detected by measuring a colorimetric read-out. For example, the liberation of a fluorophore (e.g., liberation from a FRET pair, liberation from a quencher/fluor pair, and the like) can result in a wavelength shift (and thus color shift) of a detectable signal. Thus, in some embodiments, cleavage of a probe can be detected by a color-shift. Such a shift can be expressed as a loss of an amount of signal of one color (wavelength), a gain in the amount of another color, a change in the ration of one color to another, and the like. 
     Methods for Labeling Nucleic Acid Targets 
     There are provided, in some embodiments, methods for labeling nucleic acid targets in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; and extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label. The method can comprise determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences, second molecular labels with distinct sequences, or a combination thereof, associated with the plurality of extended barcoded nucleic acid molecules, or products thereof. 
     There are provided, in some embodiments, methods for determining the numbers of nucleic acid targets in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label; and determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences, second molecular labels with distinct sequences, or a combination thereof, associated with the plurality of extended barcoded nucleic acid molecules, or products thereof. 
     There are provided, in some embodiments, methods of the generation and analysis of single-labeled nucleic acid molecules. The method can comprise amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules each comprising the first molecular label or the second molecular label, wherein determining the copy number of the nucleic acid target in the sample comprises: determining the copy number of the nucleic acid target in the sample based on the number of second molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. In some embodiments, determining the copy number of the nucleic acid target in the sample comprises: determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. The method can comprise amplifying the plurality of extended barcoded nucleic acid molecules to generate copies of the plurality of extended barcoded nucleic acid molecules, wherein determining the copy number of the nucleic acid target in the sample comprises: determining the copy number of the nucleic acid target in the sample based on (i) the number of first molecular labels with distinct sequences associated with the copies of plurality of extended barcoded nucleic acid molecules, or products thereof, and/or (ii) the number of second molecular labels with distinct sequences associated with the copies of plurality of extended barcoded nucleic acid molecules, or products thereof. 
     Also provided herein are methods, systems, compositions, and kits for determining the numbers of a nucleic acid target in a sample. In some embodiments, the method comprises: contacting copies of a nucleic acid target with a plurality of oligonucleotide barcodes, wherein each oligonucleotide barcode comprises a molecular label and a target-binding region capable of hybridizing to the nucleic acid target; extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of a reverse transcriptase and a template switch oligonucleotide comprising the target-binding region, or a portion thereof, to generate a plurality of barcoded nucleic acid molecules each comprising a sequence complementary to at least a portion of the nucleic acid target, a first molecular label, the target-binding region, and a complement of the target-binding region; hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules; extending 3′-ends of the plurality of barcoded nucleic acid molecules to generate a plurality of extended barcoded nucleic acid molecules each comprising the first molecular label and a second molecular label; amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules each comprising the first molecular label or the second molecular label; and determining the copy number of the nucleic acid target in the sample based on the number of second molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. 
     Some embodiments of the methods provided herein comprise determining the copy number of the nucleic acid target in the sample based on the number of first molecular labels with distinct sequences associated with the plurality of single-labeled nucleic acid molecules. In some embodiments, the method comprises denaturing the plurality of barcoded nucleic acid molecules prior to hybridizing the complement of the target-binding region of each barcoded nucleic acid molecule with the target-binding region of: (i) an oligonucleotide barcode of the plurality of oligonucleotide barcodes, (ii) the barcoded nucleic acid molecule itself, and/or (iii) a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules. The method can comprise denaturing the plurality of extended barcoded nucleic acid molecules prior to amplifying the plurality of extended barcoded nucleic acid molecules. Determining the copy number of the nucleic acid target can comprise determining the copy number of each of the plurality of nucleic acid targets in the sample based on the number of second molecular labels with distinct sequences associated with single-labeled nucleic acid molecules of the plurality of single-labeled nucleic acid molecules comprising a sequence of the each of the plurality of nucleic acid targets. Determining the copy number of the nucleic acid target can comprise determining the copy number of each of the plurality of nucleic acid targets in the sample based on the number of first molecular labels with distinct sequences associated with single-labeled nucleic acid molecules of the plurality of single-labeled nucleic acid molecules comprising a sequence of the each of the plurality of nucleic acid targets. The sequence of the each of the plurality of nucleic acid targets can comprise a subsequence of the each of the plurality of nucleic acid targets. The sequence of the nucleic acid target in the plurality of barcoded nucleic acid molecules can comprise a subsequence of the nucleic acid target. 
     In some embodiments, the methods comprise the addition (e.g., by a template switching reaction) of a complement of a target-binding region to an end (e.g., the 3′ end) of a barcoded nucleic acid molecule. In some embodiments, the method comprises i) intramolecular hybridization and/or ii) intermolecular hybridization of the target-binding region of an oligonucleotide barcode (or a product thereof, such as, for example, another barcoded nucleic acid molecule, or an amplicon thereof) followed by extension to generate an extended barcoded nucleic acid molecule. An extended barcoded nucleic acid molecule can be barcoded on both the 3′ and the 5′ end. In some embodiments, intramolecular hybridization of a barcoded molecule forms hairpin loops with capture mRNA transcripts on 3′ poly(dT) capture beads. mRNA molecules can be captured onto beads via the poly(A) tail binding to the target-binding region of an oligonucleotide barcode. Following hybridization, template switching can be used to attach a poly(dA) tail at the 5′ end of the captured transcript. The new poly(dA) tail can then hybridize to free capture oligonucleotides (e.g., barcodes, such as stochastic barcodes) on the same bead. After extension, the mRNA molecules can be barcoded on both the 3′ and the 5′ end. This allows generation of both 3′ and 5′ barcoded transcripts that can be sequenced on, for example, the Illumina sequencing platform. Access to barcoded 5′ sequence can allow detection of the variable region of T-cell receptor (TCR) and B-cell receptor (BCR), as well as splice variants and sequence variations that occur in the 5′ ends of the transcripts. 
       FIGS.  6 A- 6 K  show schematic illustrations of non-limiting exemplary workflows of determining the sequences of a nucleic acid target (e.g., the V(D)J region of an immune receptor) using 5′ barcoding and/or 3′ barcoding. BD® Rhapsody™ beads are solid barcoded beads that maintains integrity through a wide range of physical and chemical manipulations. Following poly(A) capture of mRNA on the beads, reverse transcription and template switching can be performed to add a poly(dA) tail to the 3′ end of the barcoded cDNA. The added poly(dA) tail allows the bead-bound cDNA to self-hybridize to oligo(dT) regions of barcodes (e.g., stochastic barcodes) on the same bead, forming a bridge-loop structure. Klenow extension of the bridge-loop can generate a new barcoded cDNA molecule that came from the same mRNA transcript, with the opposite orientation as the first barcoded cDNA, allowing both 3′ and 5′ ends to the molecular barcode to be linked. 
     The method disclosed herein can allow 3′-based and/or 5′-based sequence determination. This method can enable provide flexibility to sequence determination. In some embodiments, the method can enable immune repertoire profiling of both T cells and B cells on a Rhapsody™ system, for samples such as mouse and human samples, without changing protocol or product configuration aside from primers used. In some embodiments, 3′ and/or 5′ gene expression profiling of V(D)J can be performed. In some embodiments, both phenotypic markers and V(D)J sequence of T cell and B cells in single cell platforms can be investigated. In some embodiments, both 3′ and 5′ information of their transcripts can be captured in a single experiment. The method disclosed herein can allow V(D)J detection of both T cells and B cells (e.g., hypermutation). 
     The methods and systems described herein can be used with methods and systems using antibodies associated with (e.g., attached to or conjugated with) oligonucleotides (also referred to herein as AbOs or AbOligos). Embodiments of using AbOs to determine protein expression profiles in single cells and tracking sample origins have been described in U.S. patent application Ser. No. 15/715,028, published as U.S. Patent Application Publication No. 2018/0088112, and U.S. patent application Ser. No. 15/937,713; the content of each is incorporated by reference herein in its entirety. In some embodiments, the method disclosed herein allows V(D)J profiling of T cells and B cells, 3′ targeted, 5′ targeted, 3′ whole transcriptome amplification (WTA), 5′ WTA, protein expression profiling with AbO, and/or sample multiplexing on a single experiment.  FIG.  7    shows a non-limiting exemplary schematic illustration of performing a V(D)J workflow, an antibody-oligonucleotide (AbO) workflow, and a single cell mRNA expression profile workflow (e.g., the BD Rhapsody targeted workflow). Methods for determining the sequences of a nucleic acid target (e.g., the V(D)J region of an immune receptor) using 5′ barcoding and/or 3′ barcoding are described in U.S. patent application Ser. No. 16/588,405, filed on Sep. 30, 2019; the content of which is incorporated herein by reference in its entirety. Systems, methods, compositions, and kits for molecular barcoding on the 5′-end of a nucleic acid target have been described in U.S. patent application Ser. No. 16/588,405, published as U.S. Patent Application Publication No. 2019/0338278, the content of which is incorporated herein by reference in its entirety. The compositions (e.g. primer panels) provided herein can, in some embodiments, be employed in concert with the methods to obtain full-length V(D)J information (e.g., by Illumina sequencing on the Rhapsody system) using a combined 5′ barcoding and random priming approach described in U.S. patent application Ser. No. 17/091,639, filed on Nov. 6, 2020, entitled “USING RANDOM PRIMING TO OBTAIN FULL-LENGTH V(D)J INFORMATION FOR IMMUNE REPERTOIRE SEQUENCING”, the content of which is incorporated herein by reference in its entirety. The compositions (e.g. primer panels) provided herein can, in some embodiments, be employed in concert with random priming and extension (RPE)-based whole transcriptome analysis methods and compositions have been described in U.S. patent application Ser. No. 16/677,012; the content of which is incorporated herein by reference in its entirety. The compositions (e.g. primer panels) provided herein can, in some embodiments, be employed in concert with the blocker oligonucleotides described in U.S. patent application Ser. No. 17/163,177, filed on Jan. 29, 2021, entitled “MESOPHILIC DNA POLYMERASE EXTENSION BLOCKERS”, the content of which is incorporated herein by reference in its entirety. 
     Template-Switching Reactions 
       FIGS.  6 A- 6 K  show schematic illustrations of non-limiting exemplary workflows of determining the sequences of a nucleic acid target (e.g., the V(D)J region of an immune receptor) using 5′ barcoding and/or 3′ barcoding. A barcode (e.g., a stochastic barcode, an oligonucleotide barcode  602 ) can comprise a target binding region (e.g., a poly(dT)  604 ) that can bind to nucleic acid targets (e.g., poly-adenylated RNA transcripts  606 ) via a poly(dA) tail  608 , or other nucleic acid targets, for labeling or barcoding (e.g., unique labeling). The target-binding region can comprise a gene-specific sequence, an oligo(dT) sequence, a random multimer, or any combination thereof. In some embodiments the barcode is associated with a solid support (e.g., a particle  610 ). A plurality of barcodes  602  can be associated with particle  610 . In some embodiments, the particle is a bead. The bead can be a polymeric bead, for example a deformable bead or a gel bead, functionalized with barcodes or stochastic barcodes (such as gel beads from 10× Genomics (San Francisco, Calif.)). In some implementation, a gel bead can comprise a polymer-based gels. Gel beads can be generated, for example, by encapsulating one or more polymeric precursors into droplets. Upon exposure of the polymeric precursors to an accelerator (e.g., tetramethylethylenediamine (TEMED)), a gel bead may be generated. 
       FIG.  6 A  depicts a non-limiting exemplary embodiment of reverse transcription reaction  600   a . During reverse transcription  600   a , upon reaching the end of the oligonucleotide barcode  602 , the terminal transferase activity of an enzyme (e.g., a reverse transcriptase, such as a Moloney murine leukemia virus (MMLV)) adds a few additional nucleotides (e.g., deoxycytidine, CCC  612 ) to the 3′ end of the newly synthesized cDNA sequence strand  614   c  (the antisense sequence of RNA sequence  614   r ). These CCC bases  612  can function as an anchoring site of the template switch oligonucleotide (e.g., template switching oligonucleotide)  616 , which comprises a sequence complementary to the tailed sequence (e.g., rGrGrG  618 ). The template switch oligonucleotide  616  can comprise at least part of the target binding region  604 . Upon base pairing between the rGrGrG  618  and the appended deoxycytidine stretch  612 , the enzyme “switches” template strands, from oligonucleotide barcode  602  to the template switch oligonucleotide  616 , and continues replication to the 5′ end of the template switch oligonucleotide  616 . Thus, the resulting first strand labelled cDNA (e.g., barcoded nucleic acid molecule  620 ) contains a reverse complement sequence of the template switch oligonucleotide  616  and thus can comprise the complement (e.g., reverse complement) of the target binding region (e.g., poly(dA)  608 ). The barcoded nucleic acid molecule  620  can comprise cDNA  614   c  (the reverse complementary sequence of RNA sequence  614   r ). The reaction can be performed in the presence of one or more additives configured to reduce secondary structure (e.g., ethylene glycol). The barcoded nucleic acid molecule  620  can also comprise a number of labels. The oligonucleotide barcode  602  can include first molecular label (ML1)  622  and a sample label (e.g, partition label, cell label (CL)  624 ) for labeling the transcripts  606  and tracking sample origins of the RNA transcripts  606  (or nucleic acid targets, such as for example, antibody oligonucleotides, whether associated with antibodies or have dissociated from antibodies), respectively, along with one or more additional sequences flanking the first molecular label  622 /cell label  624  region of each barcode  602  for subsequent reactions, such as, for example, a first universal sequence  626  (e.g., Read 1 sequence). The repertoire of sequences of the molecular labels in the oligonucleotide barcodes per sample can be sufficiently large for stochastic labeling of RNA transcripts. In some embodiments, the sample label is a partition label. In some embodiments, the sample label is a cell label. The barcoded nucleic acid molecule  620  can undergo a denaturing step  600   b  (e.g., denaturing), thereby generating single-stranded barcoded nucleic acid molecule  621 . 
     In some embodiments, the first molecular label is hybridized to the second molecular label after extending the 3′-ends of the plurality of barcoded nucleic acid molecules. In some embodiments, the extended barcoded nucleic acid molecules each comprise the first molecular label, the second molecular label, the target-binding region, and the complement of the target-binding region. In some embodiments, the complement of the target-binding region is complementary to a portion of the target-binding region. In some embodiments, the target-binding region comprises a gene-specific sequence. In some embodiments, the target-binding region comprises a poly(dT) sequence. 
     The term “template switching” can refer to the ability of a reverse transcriptase to switch from an initial nucleic acid sequence template to the 3′ end of a new nucleic acid sequence template having little or no complementarity to the 3′ end of the nucleic acid synthesized from the initial template. An example of template switching is the ability of a reverse transcriptase to switch from an initial nucleic acid sequence template/primer substrate to the 3′ end of a new nucleic acid sequence template having little or no complementary to the 3′ end of the nucleic acid primer strand. Template switching allows, e.g., a DNA copy to be prepared using a reverse transcriptase that switches from an initial nucleic acid sequence template to the 3′ end of a new nucleic acid sequence template having little or no complementarity to the 3′ end of the DNA synthesized from the initial template, thereby allowing the synthesis of a continuous product DNA that directly links an adaptor sequence to a target oligonucleotide sequence without ligation. Template switching can comprise ligation of adaptor, homopolymer tailing (e.g., polyadenylation), random primer, or an oligonucleotide that the polymerase can associate with. In any of the above-mentioned embodiments, template switching may be used to introduce a target-binding region or the complement thereof. 
     In some embodiments, the reverse transcriptase is capable of terminal transferase activity. In some embodiments, the template switch oligonucleotide comprises one or more 3′ ribonucleotides. In some embodiments, the template switch oligonucleotide comprises three 3′ ribonucleotides. In some embodiments, the 3′ ribonucleotides comprise guanine. In some embodiments, the reverse transcriptase comprises a viral reverse transcriptase. In some embodiments, the viral reverse transcriptase is a murine leukemia virus (MLV) reverse transcriptase. In some embodiments, the viral reverse transcriptase is a Moloney murine leukemia virus (MMLV) reverse transcriptase. In some embodiments the template switching oligonucleotide comprises SEQ ID NO: 50. 
     The complement of a target-binding region can comprise the reverse complementary sequence of the target-binding region or can comprise the complementary sequence of the target-binding region. The complement of a molecular label can comprise a reverse complementary sequence of the molecular label or can comprise a complementary sequence of the molecular label. In some embodiments, the plurality of barcoded nucleic acid molecules can comprise barcoded deoxyribonucleic acid (DNA) molecules and/or barcoded ribonucleic acid (RNA) molecules. In some embodiments, the nucleic acid target comprises a nucleic acid molecule (e.g, ribonucleic acid (RNA), messenger RNA (mRNA), microRNA, small interfering RNA (siRNA), RNA degradation product, RNA comprising a poly(A) tail, or any combination thereof). In some embodiments, the mRNA encodes an immune receptor. The nucleic acid target can comprise a cellular component binding reagent. In some embodiments, the nucleic acid molecule is associated with the cellular component binding reagent. The method can comprise dissociating the nucleic acid molecule and the cellular component binding reagent. In some embodiments, at least 10 of the plurality of oligonucleotide barcodes comprise different molecular label sequences. Each molecular label of the plurality of oligonucleotide barcodes can comprise at least 6 nucleotides. 
     In some embodiments, the plurality of oligonucleotide barcodes are associated with a solid support. The plurality of oligonucleotide barcodes associated with the same solid support can each comprise an identical sample label. Each sample label of the plurality of oligonucleotide barcodes can comprise at least 6 nucleotides. The plurality of oligonucleotide barcodes can each comprise a cell label. Each cell label of the plurality of oligonucleotide barcodes can comprise at least 6 nucleotides. Oligonucleotide barcodes associated with the same solid support can comprise the same cell label. Oligonucleotide barcodes associated with different solid supports can comprise different cell labels. The plurality of extended barcoded nucleic acid molecules can each comprise a cell label and a complement of the cell label. The complement of the cell label can comprise a reverse complementary sequence of the cell label or a complementary sequence of the cell label. The method can comprise extending the plurality of oligonucleotide barcodes hybridized to the copies of the nucleic acid target in the presence of one or more of ethylene glycol, polyethylene glycol, 1,2-propanediol, dimethyl sulfoxide (DMSO), glycerol, formamide, 7-deaza-GTP, acetamide, tetramethylammonium chloride salt, betaine, or any combination thereof. In some embodiments, the solid support can comprise a synthetic particle. In some embodiments, the solid support can comprise a planar surface. 
     The sample can comprise a single cell, and the method can comprise associating a synthetic particle comprising the plurality of the oligonucleotide barcodes with the single cell in the sample. The method can comprise lysing the single cell after associating the synthetic particle with the single cell. Lysing the single cell can comprise heating the sample, contacting the sample with a detergent, changing the pH of the sample, or any combination thereof. In some embodiments, the synthetic particle and the single cell are in the same well. In some embodiments, the synthetic particle and the single cell are in the same droplet. In some embodiments, at least one of the plurality of oligonucleotide barcodes is immobilized on the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is partially immobilized on the synthetic particle. At least one of the plurality of oligonucleotide barcodes can be enclosed in the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is partially enclosed in the synthetic particle. In some embodiments, the synthetic particle is disruptable. The synthetic particle can comprise a bead. The bead can comprise a sepharose bead, a streptavidin bead, an agarose bead, a magnetic bead, a conjugated bead, a protein A conjugated bead, a protein G conjugated bead, a protein A/G conjugated bead, a protein L conjugated bead, an oligo(dT) conjugated bead, a silica bead, a silica-like bead, an anti-biotin microbead, an anti-fluorochrome microbead, or any combination thereof. The synthetic particle can comprise a material selected from the group consisting of polydimethylsiloxane (PDMS), polystyrene, glass, polypropylene, agarose, gelatin, hydrogel, paramagnetic, ceramic, plastic, glass, methylstyrene, acrylic polymer, titanium, latex, Sepharose, cellulose, nylon, silicone, and any combination thereof. In some embodiments, the synthetic particle can comprise a disruptable hydrogel particle. Each of the plurality of oligonucleotide barcodes can comprise a linker functional group, the synthetic particle can comprise a solid support functional group, and/or the support functional group and the linker functional group can be associated with each other. In some embodiments, the linker functional group and the support functional group are individually selected from the group consisting of C6, biotin, streptavidin, primary amine(s), aldehyde(s), ketone(s), and any combination thereof. 
     Intramolecular Hybridization of Barcoded Nucleic Acid Molecules 
     In some embodiments, hybridizing the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of the barcoded nucleic acid molecule itself comprises intramolecular hybridization of the target-binding region and the complement of the target-binding region within a barcoded nucleic acid molecule to form a stem loop. In some embodiments, the second molecular label is the complement of the first molecular label. 
     The workflow can comprise intramolecular hybridization of a single-stranded barcoded nucleic acid molecule  621  as depicted in the non-limiting exemplary  FIG.  6 B  schematic illustrations. The workflow can comprise intramolecular hybridization  600   c   1  of the target-binding region  604  and the complement of the target-binding region  608  within a single-stranded barcoded nucleic acid molecule  621  to form a stem loop. The workflow can comprise extending  600   c   2  the 3′-end of the stem loop of single-stranded barcoded nucleic acid molecule  621  to generate extended barcoded nucleic acid molecule  620   c . The extended barcoded nucleic acid molecule  620   c  can comprise a complement (e.g., reverse complement) of the first molecular label  622   rc , a complement (e.g., reverse complement) of the cell label  624   rc , and/or a complement (e.g., reverse complement) of the first universal sequence  626   rc . The workflow can comprise denaturing  600   c   3  the extended barcoded nucleic acid molecule  620   c  to generate a single-stranded extended barcoded nucleic acid molecule  620   cd . In some embodiments, intermolecular hybridization  600   c   1  and/or extending  600   c   2  is performed in the presence of a high salt buffer and/or PEG. In some embodiments, extension is performed using a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity (e.g., a Klenow Fragment). 
     Single-stranded extended barcoded nucleic acid molecule  620   cd  can comprise a barcode (e.g., a cell label and a molecular label) on both the 5′ end and 3′ end of a target nucleic acid molecule (e.g., transcript), thereby enabling more extensive analysis of the target nucleic acid molecule as compared to an analysis of a target nucleic acid molecule with only one barcode on one end with regards to sequence identification, transcript counting, alternative splicing analysis, mutation screening, and/or full length sequencing. Single-stranded extended barcoded nucleic acid molecule  620   cd  can serve as a template for one or more amplification reactions (e.g., PCR), such as, for example, the non-limiting exemplary amplification scheme depicted in  FIGS.  6 C- 6 D . The amplification(s) can comprise target-specific (e.g., gene-specific) cDNA amplification. For example, single-stranded extended barcoded nucleic acid molecule  620   cd  can undergo a first round of amplification (“PCR1”)  600   c   4  employing a universal oligonucleotide primer  646  comprising a sequence of the first universal sequence (or a complement thereof) and a target-specific primer (e.g., one or more first amplification primers, target-specific primer  648  and/or target-specific primer  650 ). PCR1 can comprise amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules using a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more first amplification primers. PCR1  600   c   4  can comprise amplifying the 5′ region of the single-stranded extended barcoded nucleic acid molecule  620   cd  with universal oligonucleotide primer  646  and target-specific primer  648 , thereby producing single-labeled nucleic acid molecule  620   c   1  comprising first molecular label  622 , cell label  624 , first universal sequence  626  and partial cDNA  614   c   1  (the length of which depends on the binding site of target-specific primer  648  within the cDNA  614   c ). PCR1  600   c   4  can comprise amplifying the 3′ region of the single-stranded extended barcoded nucleic acid molecule  620   cd  with universal oligonucleotide primer  646  and target-specific primer  650 , thereby producing single-labeled nucleic acid molecule  620 cas 1  comprising first molecular label  622 , cell label  624 , first universal sequence  626  and partial antisense cDNA  614 cas 1  (the length of which depends on the binding site of target-specific primer  650  within the cDNA  614   c ). PCR1  600   c   4  can comprise 1-30 cycles (e.g., 15 cycles). 
     The workflow can comprise a second round of amplification (“PCR2”)  600   c   5  employing universal oligonucleotide primer  646  and a nested target-specific primer (e.g., target-specific primer  652  and/or target-specific primer  654 ). PCR2 can comprise amplifying the plurality of single-labeled nucleic acid molecules using primers capable of hybridizing to the first universal sequence, or a complement thereof, and one or more second amplification primers, thereby generating a first plurality of barcoded amplicons. Target-specific primer  652  and/or target-specific primer  654  can include overhangs, which can include, or be, for example, a second universal sequence  638  (e.g., Read 2 sequence, a universal PCR handle). PCR2  600   c   5  can comprise amplifying single-labeled nucleic acid molecule  620   c   1  with universal oligonucleotide primer  646  and nested target-specific primer  654  (e.g, one or more second amplification primers), thereby producing single-labeled nucleic acid molecule  620   c   2  (e.g., a first plurality of barcoded amplicons) comprising first molecular label  622 , cell label  624 , first universal sequence  626 , second universal sequence  638 , and partial cDNA  614   c   2  (the length of which depends on the binding site of nested target-specific primer  654  within the partial cDNA  614   c   1 ). PCR2  600   c   5  can comprise amplifying single-labeled nucleic acid molecule  620 cas 1  with universal oligonucleotide primer  646  and nested target-specific primer  652 , thereby producing single-labeled nucleic acid molecule  620 cas 2  comprising first molecular label  622 , cell label  624 , first universal sequence  626 , second universal sequence  638 , and partial antisense cDNA  614 cas 2  (the length of which depends on the binding site of nested target-specific primer  652  within the partial antisense cDNA  614 cas 1 ). PCR2  600   c   5  can comprise 1-30 cycles (e.g., 15 cycles). In some embodiments, target-specific primers  648 ,  650 ,  652 , and/or  654  bind the constant region, variable region, diversity region, and/or junction region of an immune receptor. 
     The workflow can comprise a third round of amplification (“PCR3”)  600   c   6 . PCR3  600   c   6  can comprise library amplification of single-labeled nucleic acid molecule  620 cas 2  and/or single-labeled nucleic acid molecule  620   c   2  with sequencing library amplification primers  656  and  658 . Sequencing library amplification primers  656  can  658  can anneal to first universal sequence  626  and second universal sequence  638  (or complements thereof), respectively. PCR3  600   c   6  can add sequencing adapters (e.g., P 5   640  and P 7   642 ) and sample index  644  (e.g., i5, i7) via overhangs in sequencing library amplification primers  656  and  658 . Library amplicons  620 cas 3  and/or  620   c   3  can be sequenced and subjected to downstream methods of the disclosure. Sequencing using 150 bp×2 sequencing can reveal the cell label, unique molecular label and/or gene (or a partial sequence of the gene) on read 1, the gene (or a partial sequence of the gene) on read 2, and the sample index on index 1 read and/or index 2 read. PCR3  600   c   6  can comprise 1-30 cycles (e.g., 15 cycles). 
     In some embodiments, 3′ and/or 5′ expression profiling of the V(D)J region of an immune receptor can be performed. In some embodiments, both phenotypic markers and immune receptor V(D)J sequence(s) of T cells and/or B cells in single cell platforms can be investigated. In some embodiments, both the 3′ and 5′ information of their transcripts can be captured in a single experiment. The method disclosed herein can allow V(D)J detection of both T cells and B cells (e.g., hypermutation). In some embodiments, both the 3′ and 5′ regions of extended barcoded nucleic acid molecule  620   cd  are amplified. In some embodiments, only the 5′ region of extended barcoded nucleic acid molecule  620   cd  is amplified. In some embodiments, only the 3′ region of extended barcoded nucleic acid molecule  620   cd  is amplified. In some embodiments one or more of the amplification reactions comprises multiplex PCR. For example, both the 3′ and 5′ regions of extended barcoded nucleic acid molecule  620   cd  can be amplified simultaneously (e.g., multiplex PCR). In some embodiments the workflow comprises multiplex PCR employing a panel of target-specific PCR1 primers and/or a panel of target-specific PCR2 primers. In some embodiments, the targets comprise BCRs, TCRs, and/or immune-related transcripts. In some embodiments, the panel of target-specific PCR1 primers (e.g., one or more first amplification primers) comprises one or more primers having a sequence that exhibits at least about 80% identity to any one of the sequences listed in Tables 1 and/or 3. In some embodiments, the panel of target-specific PCR2 primers (e.g., one or more second amplification primers) comprises one or more primers having a sequence that exhibits at least about 80% identity to any one of the sequences listed in Tables 2, 4, 5 and/or 6. 
     Intermolecular Hybridization of Barcoded Nucleic Acid Molecules with Barcoded Nucleic Acid Molecules 
     In some embodiments, hybridizing the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules comprises intermolecular hybridization of the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of a different barcoded nucleic acid molecule of the plurality of barcoded nucleic acid molecules. In some embodiments, the sequence of the second molecular label is different from the sequence of the first molecular label, and wherein the second molecular label is not a complement of the first molecular label. 
     The workflow can comprise intermolecular hybridization of single-stranded barcoded nucleic acid molecule  621  with a distinct barcoded nucleic acid molecule  628  as depicted in the non-limiting exemplary  FIGS.  6 E- 6 F  schematic illustrations. Distinct barcoded nucleic acid molecule  628  can comprise cDNA  630   c , second molecular label  632 , cell label  624 , and first universal sequence  626 . The sequence of second molecular label  632  of barcoded nucleic acid molecule  628  can be different from the sequence of the first molecular label  622  of single-stranded barcoded nucleic acid molecule  621  (e.g., not a complement). The target-binding region  604 , cell label  624  and/or first universal sequence  626  of barcoded nucleic acid molecule  628  can be the same as (or a complement thereof) the target-binding region  604 , cell label  624  and/or first universal sequence  626  of single-stranded barcoded nucleic acid molecule  621 . The workflow can comprise, in some embodiments, intermolecular hybridization  600   d   1  of the complement of the target-binding region  608  of single-stranded barcoded nucleic acid molecule  621  with the target-binding region  604  of barcoded nucleic acid molecule  628 . The workflow can comprise extending  600   d   2  the 3′-end of single-stranded barcoded nucleic acid molecule  621  to generate extended barcoded nucleic acid molecule  620   d . The extended barcoded nucleic acid molecule  620   d  can comprise a complement (e.g., reverse complement) of the second molecular label  632   rc , a complement (e.g., reverse complement) of the cell label  624   rc , and/or a complement (e.g., reverse complement) of the first universal sequence  626   rc . The workflow can comprise denaturing  600   d   3  the extended barcoded nucleic acid molecule  620   d  to generate a single-stranded extended barcoded nucleic acid molecule  620   dd . In some embodiments, intermolecular hybridization  600   d   1  and/or extending  600   d   2  is performed in the presence of a high salt buffer and/or PEG. In some embodiments, extension is performed using a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity (e.g., a Klenow Fragment). 
     Single-stranded extended barcoded nucleic acid molecule  620   dd  can comprise a barcode (e.g., a cell label and a molecular label) on both the 5′ end and 3′ end of a target nucleic acid molecule (e.g., transcript), thereby enabling more extensive analysis of the target nucleic acid molecule as compared to an analysis of a target nucleic acid molecule with only one barcode on one end with regards to sequence identification, transcript counting, alternative splicing analysis, mutation screening, and/or full length sequencing. Single-stranded extended barcoded nucleic acid molecule  620   dd  can serve as a template for one or more amplification reactions (e.g., PCR), such as, for example, the non-limiting exemplary amplification scheme depicted in  FIGS.  6 G- 6 H . The amplification(s) can comprise target-specific (e.g., gene-specific) cDNA amplification. For example, single-stranded extended barcoded nucleic acid molecule  620   dd  can undergo a first round of amplification (“PCR1”)  600   d   4  employing a universal oligonucleotide primer  646  comprising a sequence of the first universal sequence (or a complement thereof) and a target-specific primer (e.g., one or more first amplification primers, target-specific primer  648  and/or target-specific primer  650 ). PCR1 can comprise amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules using a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more first amplification primers. PCR1  600   d   4  can comprise amplifying the 5′ region of the single-stranded extended barcoded nucleic acid molecule  620   dd  with universal oligonucleotide primer  646  and target-specific primer  648 , thereby producing single-labeled nucleic acid molecule  620   d   1  comprising first molecular label  622 , cell label  624 , first universal sequence  626  and partial cDNA  614   c   1  (the length of which depends on the binding site of target-specific primer  648  within the cDNA  614   c ). PCR1  600   d   4  can comprise amplifying the 3′ region of the single-stranded extended barcoded nucleic acid molecule  620   dd  with universal oligonucleotide primer  646  and target-specific primer  650 , thereby producing single-labeled nucleic acid molecule  620 das 1  comprising second molecular label  632 , cell label  624 , first universal sequence  626  and partial antisense cDNA  614 cas 1  (the length of which depends on the binding site of target-specific primer  650  within the cDNA  614   c ). PCR1  600   d   4  can comprise 1-30 cycles (e.g., 15 cycles). 
     The workflow can comprise a second round of amplification (“PCR2”)  600   d   5  employing universal oligonucleotide primer  646  and a nested target-specific primer (e.g., target-specific primer  652  and/or target-specific primer  654 ). PCR2 can comprise amplifying the plurality of single-labeled nucleic acid molecules using primers capable of hybridizing to the first universal sequence, or a complement thereof, and one or more second amplification primers, thereby generating a first plurality of barcoded amplicons. Target-specific primer  652  and/or target-specific primer  654  can include overhangs, which can include, or be, for example, a second universal sequence  638  (e.g., Read 2 sequence, a universal PCR handle). PCR2  600   d   5  can comprise amplifying single-labeled nucleic acid molecule  620   d   1  with universal oligonucleotide primer  646  and nested target-specific primer  654  (e.g, one or more second amplification primers), thereby producing single-labeled nucleic acid molecule  620   d   2  (e.g., a first plurality of barcoded amplicons) comprising first molecular label  622 , cell label  624 , first universal sequence  626 , second universal sequence  638 , and partial cDNA  614   c   2  (the length of which depends on the binding site of nested target-specific primer  654  within the cDNA  614   c   1 ). PCR2  600   d   5  can comprise amplifying single-labeled nucleic acid molecule  620 das 1  with universal oligonucleotide primer  646  and nested target-specific primer  652 , thereby producing single-labeled nucleic acid molecule  620 das 2  comprising second molecular label  632 , cell label  624 , first universal sequence  626 , second universal sequence  638 , and partial antisense cDNA  614 cas 2  (the length of which depends on the binding site of nested target-specific primer  652  within the partial antisense cDNA  614 cas 1 ). PCR2  600   d   5  can comprise 1-30 cycles (e.g., 15 cycles). In some embodiments, target-specific primers  648 ,  650 ,  652 , and/or  654  bind the constant region, variable region, diversity region, and/or junction region of an immune receptor. 
     The workflow can comprise a third round of amplification (“PCR3”)  600   d   6 . PCR3  600   d   6  can comprise library amplification of single-labeled nucleic acid molecule  620 das 2  and/or single-labeled nucleic acid molecule  620   d   2  with sequencing library amplification primers  656  and  658 . Sequencing library amplification primers  656  can  658  can anneal to first universal sequence  626  and second universal sequence  638  (or complements thereof), respectively. PCR3  600   d   6  can add sequencing adapters (e.g., P 5   640  and P 7   642 ) and sample index  644  (e.g., i5, i7) via overhangs in sequencing library amplification primers  656  and  658 . Library amplicons  620 das 3  and/or  620   d   3  can be sequenced and subjected to downstream methods of the disclosure. Sequencing using 150 bp×2 sequencing can reveal the cell label, unique molecular label and/or gene (or a partial sequence of the gene) on read 1, the gene (or a partial sequence of the gene) on read 2, and the sample index on index 1 read and/or index 2 read. PCR3  600   d   6  can comprise 1-30 cycles (e.g., 15 cycles). 
     In some embodiments, 3′ and/or 5′ expression profiling of the V(D)J region of an immune receptor can be performed. In some embodiments, both phenotypic markers and immune receptor V(D)J sequence(s) of T cells and/or B cells in single cell platforms can be investigated. In some embodiments, both the 3′ and 5′ information of their transcripts can be captured in a single experiment. The method disclosed herein can allow V(D)J detection of both T cells and B cells (e.g., hypermutation). In some embodiments, both the 3′ and 5′ regions of extended barcoded nucleic acid molecule  620   dd  are amplified. In some embodiments, only the 5′ region of extended barcoded nucleic acid molecule  620   dd  is amplified. In some embodiments, only the 3′ region of extended barcoded nucleic acid molecule  620   dd  is amplified. In some embodiments one or more of the amplification reactions comprises multiplex PCR. For example, both the 3′ and 5′ regions of extended barcoded nucleic acid molecule  620   dd  can be amplified simultaneously (e.g., multiplex PCR). In some embodiments the workflow comprises multiplex PCR employing a panel of target-specific PCR1 primers and/or a panel of target-specific PCR2 primers. In some embodiments, the targets comprise BCRs, TCRs, and/or immune-related transcripts. In some embodiments, the panel of target-specific PCR1 primers (e.g., one or more first amplification primers) comprises one or more primers having a sequence that exhibits at least about 80% identity to any one of the sequences listed in Tables 1 and/or 3. In some embodiments, the panel of target-specific PCR2 primers (e.g., one or more second amplification primers) comprises one or more primers having a sequence that exhibits at least about 80% identity to any one of the sequences listed in Tables 2, 4, 5 and/or 6. 
     Intermolecular Hybridization of Barcoded Nucleic Acid Molecules with Oligonucleotide Barcodes 
     In some embodiments, hybridizing the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of an oligonucleotide barcode of the plurality of oligonucleotide barcodes comprises intermolecular hybridization of the complement of the target-binding region of a barcoded nucleic acid molecule with the target-binding region of an oligonucleotide barcode of the plurality of oligonucleotide barcodes. In some embodiments, the second molecular label is a different from the first molecular label, and wherein the second molecular label is not a complement of the first molecular label. In some embodiments, the method comprises extending the 3′ ends of the oligonucleotide barcodes hybridized to the complement of the target-binding region of the barcoded nucleic acid molecule to generate a plurality of extended barcoded nucleic acid molecules each comprising a complement of the first molecular label and a second molecular label. In some embodiments, the sequence of the second molecular label is different from the sequence of the first molecular label, wherein the wherein the second molecular label is not a complement of the first molecular label. 
     The workflow can comprise intermolecular hybridization of single-stranded barcoded nucleic acid molecule  621  with distinct oligonucleotide barcode  634  as depicted in the non-limiting exemplary  FIGS.  6 I- 6 J  schematic illustrations. Distinct oligonucleotide barcode  634  can comprise second molecular label  636 , cell label  624 , and first universal sequence  626 . The sequence of second molecular label  636  of oligonucleotide barcode  634  can be different from the sequence of the first molecular label  622  of single-stranded barcoded nucleic acid molecule  621  (e.g., not a complement). The target-binding region  604 , cell label  624  and/or first universal sequence  626  of oligonucleotide barcode  634  can be the same as (or a complement thereof) the target-binding region  604 , cell label  624  and/or first universal sequence  626  of single-stranded barcoded nucleic acid molecule  621 . The workflow can comprise, in some embodiments, intermolecular hybridization  600   e   1  of the complement of the target-binding region  608  of single-stranded barcoded nucleic acid molecule  621  with the target-binding region  604  of oligonucleotide barcode  634 . The workflow can comprise extending  600   e   2  the 3′-end of single-stranded barcoded nucleic acid molecule  621  to generate extended barcoded nucleic acid molecule  620   e   1 . The extended barcoded nucleic acid molecule  620   e   1  can comprise a complement (e.g., reverse complement) of the second molecular label  636   rc , a complement (e.g., reverse complement) of the cell label  624   rc , a complement (e.g., reverse complement) of the first universal sequence  626   rc , and/or cDNA  614   c . The workflow can comprise denaturing  600   e   3  the extended barcoded nucleic acid molecule  620   e   1  to generate a single-stranded extended barcoded nucleic acid molecule  620   e   1   d . The workflow can comprise extending  600   e   2  the 3′-end of oligonucleotide barcode  634  to generate extended barcoded nucleic acid molecule  620   e   2 . The extended barcoded nucleic acid molecule  620   e   2  can comprise a complement (e.g., reverse complement) of the first molecular label  622   rc , a complement (e.g., reverse complement) of the cell label  624   rc , a complement (e.g., reverse complement) of the first universal sequence  626   rc , and/or antisense cDNA  614 cas. The workflow can comprise denaturing  600   e   3  the extended barcoded nucleic acid molecule  620   e   2  to generate a single-stranded extended barcoded nucleic acid molecule  620   e   2   d . In some embodiments, intermolecular hybridization  600   e   1  and/or extending  600   e   2  is performed in the presence of a high salt buffer and/or PEG. In some embodiments, extension is performed using a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity (e.g., a Klenow Fragment). 
     Single-stranded extended barcoded nucleic acid molecule  620   e   1   d  and single-stranded extended barcoded nucleic acid molecule  620   e   2   d  can comprise a barcode (e.g., a cell label and a molecular label) on both the 5′ end and 3′ end of a target nucleic acid molecule (e.g., transcript), thereby enabling more extensive analysis of the target nucleic acid molecule as compared to an analysis of a target nucleic acid molecule with only one barcode on one end with regards to sequence identification, transcript counting, alternative splicing analysis, mutation screening, and/or full length sequencing. Single-stranded extended barcoded nucleic acid molecule  620   e   1   d  and single-stranded extended barcoded nucleic acid molecule  620   e   2   d  can serve as a template for one or more amplification reactions (e.g., PCR). The amplification(s) can comprise target-specific (e.g., gene-specific) cDNA amplification. PCR1 can comprise amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules using a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more first amplification primers. PCR2 can comprise amplifying the plurality of single-labeled nucleic acid molecules using primers capable of hybridizing to the first universal sequence, or a complement thereof, and one or more second amplification primers, thereby generating a first plurality of barcoded amplicons. In some embodiments, single-stranded extended barcoded nucleic acid molecule  620   e   1   d  and/or single-stranded extended barcoded nucleic acid molecule  620   e   2   d  can undergo two or more rounds of PCR amplification (e.g., PCR1  600   d   4 , PCR2  600   d   5 , and/or PCR3  600   d   6  as depicted in  FIGS.  6 G- 6 H ). In some embodiments, single-stranded extended barcoded nucleic acid molecule  620   e   1   d  and/or single-stranded extended barcoded nucleic acid molecule  620   e   2   d  can serve as a template for a single amplification, such as, for example, the non-limiting exemplary amplification scheme depicted in  FIG.  6 K  (PCR  600   e   4 ). PCR  600   e   4  can add sequencing adapters (e.g., P 5   640  and P 7   642 ) and sample index  644  (e.g., i5, i7) via overhangs in primers  660 ,  662 , and  664 . PCR  600   e   4  can comprise amplifying the single-stranded extended barcoded nucleic acid molecule  620   e   1   d  with primer  664  (annealing to the first universal sequence or a complement thereof) and target-specific primer  660 , thereby producing single-labeled nucleic acid molecule  620   e   1   c  comprising first molecular label  622 , cell label  624 , first universal sequence  626  and partial cDNA  614   c   1   e  (the length of which depends on the binding site of target-specific primer  660  within the cDNA  614   c ). PCR  600   e   4  can comprise amplifying the single-stranded extended barcoded nucleic acid molecule  620   e   2   d  with primer  664  (annealing to the first universal sequence or a complement thereof) and target-specific primer  662 , thereby producing single-labeled nucleic acid molecule  620   e   2   c  comprising second molecular label  636 , cell label  624 , first universal sequence  626  and partial antisense cDNA  614 cas 1   e  (the length of which depends on the binding site of target-specific primer  662  within the antisense cDNA  614 cas). Library amplicons  620   e   1   c  and/or  620   e   2   c  can be sequenced and subjected to downstream methods of the disclosure. Sequencing using 150 bp×2 sequencing can reveal the cell label, unique molecular label and/or gene (or a partial sequence of the gene) on read 1, the gene (or a partial sequence of the gene) on read 2, and the sample index on index 1 read and/or index 2 read. PCR  600   e   4  can comprise 1-30 cycles (e.g., 15 cycles). In some embodiments, target-specific primers  660  and/or  662  bind the constant region, variable region, diversity region, and/or junction region of an immune receptor. 
     In some embodiments, 3′ and/or 5′ expression profiling of the V(D)J region of an immune receptor can be performed. In some embodiments, both phenotypic markers and immune receptor V(D)J sequence(s) of T cells and/or B cells in single cell platforms can be investigated. In some embodiments, both the 3′ and 5′ information of transcripts can be captured in a single experiment. The method disclosed herein can allow V(D)J detection of both T cells and B cells (e.g., hypermutation). In some embodiments, both the 3′ and 5′ regions of extended barcoded nucleic acid molecule(s)  620   e   1   d  and/or  620   e   2   d  are amplified. In some embodiments, only the 5′ region of extended barcoded nucleic acid molecule(s)  620   e   1   d  and/or  620   e   2   d  are amplified. In some embodiments, only the 3′ region of extended barcoded nucleic acid molecule(s)  620   e   1   d  and/or  620   e   2   d  are amplified. In some embodiments one or more of the amplification reactions comprises multiplex PCR. For example, both the 3′ and 5′ regions of extended barcoded nucleic acid molecule(s)  620   e   1   d  and/or  620   e   2   d  can be amplified simultaneously (e.g., multiplex PCR). In some embodiments the workflow comprises multiplex PCR employing a panel of target-specific PCR1 primers and/or a panel of target-specific PCR2 primers. In some embodiments, the targets comprise BCRs, TCRs, and/or immune-related transcripts. In some embodiments, the panel of target-specific PCR1 primers (e.g., one or more first amplification primers) comprises one or more primers having a sequence that exhibits at least about 80% identity to any one of the sequences listed in Tables 1 and/or 3. In some embodiments, the panel of target-specific PCR2 primers (e.g., one or more second amplification primers) comprises one or more primers having a sequence that exhibits at least about 80% identity to any one of the sequences listed in Tables 2, 4, 5 and/or 6. 
     Immune Repertoire Profiling 
     There are provided, in some embodiments, methods of 3′ and/or 5′ expression profiling of the V(D)J region of immune receptors. In some embodiments, the sample comprises a single cell. In some embodiments, the sample comprises a plurality of cells, a plurality of single cells, a tissue, a tumor sample, or any combination thereof. A single cell can comprise an immune cell. In some embodiments, the immune cell is a B cell or a T cell. In some embodiments, a single cell can comprise a circulating tumor cell. In some embodiments, each oligonucleotide barcode can comprise a first universal sequence. In some embodiments, the plurality of extended barcoded nucleic acid molecules comprises a first universal sequence and a complement of the first universal sequence. In some embodiments, amplifying the plurality of extended barcoded nucleic acid molecules to generate copies of the plurality of extended barcoded nucleic acid molecules comprises using a primer capable of hybridizing to the first universal sequence, or a complement thereof. 
     Amplifying the plurality of extended barcoded nucleic acid molecules to generate a plurality of single-labeled nucleic acid molecules can comprise using a primer capable of hybridizing to the first universal sequence, or a complement thereof, and one or more first amplification primers. 
     The one or more first amplification primers can comprise: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 10-17, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 10-17; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 18-20, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 18-20. 
     The one or more first amplification primers can comprise: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 1, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 1; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 2, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 2; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 3, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 3; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises a sequence of SEQ ID NO: 4, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to SEQ ID NO: 4. 
     The method can comprise amplifying the plurality of single-labeled nucleic acid molecules using primers capable of hybridizing to the first universal sequence, or a complement thereof, and one or more second amplification primers, thereby generating a first plurality of barcoded amplicons. 
     The one or more second amplification primers can comprise: one or more primers capable of hybridizing to a constant domain of an immunoglobulin heavy chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 21-28 and 37-44, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 21-28 and 37-44; and one or more primers capable of hybridizing to a constant domain of an immunoglobulin light chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 29-31 and 45-47, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 29-31 and 45-47. 
     The one or more second amplification primers can comprise: one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Alpha Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 5 and 32, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 5 and 32; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Beta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 6 and 33, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 6 and 33; one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Delta Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 7 and 34, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 7 and 34; and one or more primers capable of hybridizing to a constant domain of a T Cell Receptor Gamma Chain, wherein the one or more primers comprises any one of the sequences of SEQ ID NOS: 8-9 and 35-36, or a sequence that exhibits at least about 80% (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values) identity to any one of the sequences of SEQ ID NOS: 8-9 and 35-36. 
     In some embodiments, the first amplification primer and/or the second amplification primer is a target-specific primer, and wherein the target-specific primer specifically hybridizes to a constant region of an immune receptor. In some embodiments, the immune receptor is a T cell receptor (TCR) and/or a B cell receptor (BCR) receptor, and optionally the TCR comprises TCR alpha chain, TCR beta chain, TCR gamma chain, TCR delta chain, or any combination thereof; and the BCR receptor comprises BCR heavy chain and/or BCR light chain. Extending 3′-ends of the plurality of barcoded nucleic acid molecules can comprise extending 3′-ends of the plurality of barcoded nucleic acid molecules using a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity, and optionally the DNA polymerase comprises a Klenow Fragment. 
     The method can comprise: obtaining sequence information of the plurality of extended barcoded nucleic acid molecules, or products thereof. Obtaining the sequence information can comprise attaching sequencing adaptors to the plurality of extended barcoded nucleic acid molecules, or products thereof. Obtaining the sequence information can comprise attaching sequencing adaptors to the plurality of single-labeled nucleic acid molecules, or products thereof. Obtaining the sequence information can comprise attaching sequencing adaptors to the first plurality of barcoded amplicons, or products thereof. 
     Obtaining the sequence information can comprise obtaining the sequence information of the BCR light chain and the BCR heavy chain of a single cell. The sequence information of the BCR light chain and the BCR heavy chain can comprise the sequence of the complementarity determining region 1 (CDR1), the CDR2, the CDR3, or any combination thereof, of the BCR light chain and/or the BCR heavy chain. The method can comprise pairing the BCR light chain and the BCR heavy chain of the single cell based on the obtained sequence information. The sample can comprise a plurality of single cells, and the method can comprise pairing the BCR light chain and the BCR heavy chain of at least 50% of the single cells based on the obtained sequence information. In some embodiments, the percentage of single cells of a sample wherein the BCR light chain and the BCR heavy chain are paired according the methods provided herein can be, or be about, 0.000000001%, 0.00000001%, 0.0000001%, 0.000001%, 0.00001%, 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values. In some embodiments, the percentage of single cells of a sample wherein the BCR light chain and the BCR heavy chain are paired according the methods provided herein can be at least, or at most, 0.000000001%, 0.00000001%, 0.0000001%, 0.000001%, 0.00001%, 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. 
     Obtaining the sequence information can comprise obtaining the sequence information of the TCR alpha chain and the TCR beta chain of a single cell. In some embodiments, the sequence information of the TCR alpha chain and the TCR beta chain can comprise the sequence of the complementarity determining region 1 (CDR1), the CDR2, the CDR3, or any combination thereof, of the TCR alpha chain and/or the TCR beta chain. In some embodiments, the method can comprise pairing the TCR alpha chain and the TCR beta chain of the single cell based on the obtained sequence information. In some embodiments, the sample can comprise a plurality of single cells, and the method can comprise pairing the TCR alpha chain and the TCR beta chain of at least 50% of the single cells based on the obtained sequence information. In some embodiments, the percentage of single cells of a sample wherein the TCR alpha chain and the TCR beta chain are paired according the methods provided herein can be, or be about, 0.000000001%, 0.00000001%, 0.0000001%, 0.000001%, 0.00001%, 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values. In some embodiments, the percentage of single cells of a sample wherein the TCR alpha chain and the TCR beta chain are paired according the methods provided herein can be at least, or at most, 0.000000001%, 0.00000001%, 0.0000001%, 0.000001%, 0.00001%, 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. 
     Obtaining the sequence information can comprise obtaining the sequence information of the TCR gamma chain and the TCR delta chain of a single cell. The sequence information of the TCR gamma chain and the TCR delta chain can comprise the sequence of the complementarity determining region 1 (CDR1), the CDR2, the CDR3, or any combination thereof, of the TCR gamma chain and/or the TCR delta chain. The method can comprise pairing the TCR gamma chain and the TCR delta chain of the single cell based on the obtained sequence information. The sample can comprise a plurality of single cells, and the method can comprise pairing the TCR gamma chain and the TCR delta chain of at least 50% of the single cells based on the obtained sequence information. In some embodiments, the percentage of single cells of a sample wherein the TCR delta chain and the TCR gamma chain are paired according the methods provided herein can be, or be about, 0.000000001%, 0.00000001%, 0.0000001%, 0.000001%, 0.00001%, 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a number or a range between any two of these values. In some embodiments, the percentage of single cells of a sample wherein the TCR delta chain and the TCR gamma chain are paired according the methods provided herein can be at least, or at most, 0.000000001%, 0.00000001%, 0.0000001%, 0.000001%, 0.00001%, 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. 
     Kits for Barcoding on the 5′ and 3′ Ends of Nucleic Acid Targets 
     Disclosed herein include kits. The kit can comprise one or more the primers (e.g., primer panels) disclosed herein. In some embodiments, the kit comprises: a plurality of oligonucleotide barcodes, wherein each of the plurality of oligonucleotide barcodes comprises a molecular label and a target-binding region, and wherein at least 10 of the plurality of oligonucleotide barcodes comprise different molecular label sequences; a reverse transcriptase; a template switching oligonucleotide comprising the target-binding region, or a portion thereof; and a DNA polymerase lacking at least one of 5′ to 3′ exonuclease activity and 3′ to 5′ exonuclease activity. In some embodiments, the DNA polymerase comprises a Klenow Fragment. In some embodiments, the reverse transcriptase comprises a viral reverse transcriptase, for example a murine leukemia virus (MLV) reverse transcriptase or a Moloney murine leukemia virus (MMLV) reverse transcriptase. In some embodiments, the template switch oligonucleotide comprises one or more 3′ ribonucleotides, for example three 3′ ribonucleotides. In some embodiments, the 3′ ribonucleotides comprise guanine. In some embodiments, the kit comprises one or more of ethylene glycol, polyethylene glycol, 1,2- propanediol, dimethyl sulfoxide (DMSO), glycerol, formamide, 7-deaza-GTP, acetamide, tetramethylammonium chloride salt, betaine, or any combination thereof. 
     The kit, in some embodiments, comprises a buffer and/or a cartridge. In some embodiments, the kit comprises one or more reagents for a reverse transcription reaction, and/or one or more reagents for an amplification reaction. In some embodiments, the target-binding region comprises a gene-specific sequence, an oligo(dT) sequence, a random multimer, or any combination thereof. In some embodiments, the oligonucleotide barcode comprises an identical sample label and/or an identical cell label. In some embodiments, at least one, or each of the sample label, cell label and/or molecular label of the plurality of oligonucleotide barcodes comprise at least 6 nucleotides. At least one of the plurality of oligonucleotide barcodes can be immobilized (e.g., partially immobilized) on the synthetic particle. In some embodiments, at least one of the plurality of oligonucleotide barcodes is enclosed (e.g., partially enclosed) in the synthetic particle. In some embodiments, the synthetic particle is disruptable. In some embodiments, the synthetic particle comprises a bead, for example a sepharose bead, a streptavidin bead, an agarose bead, a magnetic bead, a conjugated bead, a protein A conjugated bead, a protein G conjugated bead, a protein A/G conjugated bead, a protein L conjugated bead, an oligo(dT) conjugated bead, a silica bead, a silica-like bead, an anti-biotin microbead, an anti-fluorochrome microbead, or any combination thereof. In some embodiments, the synthetic particle comprises polydimethylsiloxane (PDMS), polystyrene, glass, polypropylene, agarose, gelatin, hydrogel, paramagnetic, ceramic, plastic, glass, methylstyrene, acrylic polymer, titanium, latex, sepharose, cellulose, nylon, silicone, or any combination thereof. In some embodiments, the synthetic particle comprises a disruptable hydrogel particle. In some embodiments, each of the plurality of oligonucleotide barcodes comprises a linker functional group, the synthetic particle comprises a solid support functional group, and/or the support functional group and the linker functional group are associated with each other. In some embodiments, the linker functional group and the support functional group are individually selected from the group consisting of C6, biotin, streptavidin, primary amine(s), aldehyde(s), ketone(s), and any combination thereof. 
     EXAMPLES 
     Some aspects of the embodiments discussed above are disclosed in further detail in the following examples, which are not in any way intended to limit the scope of the present disclosure. 
     Example 1 
     V(D)J Protocol 
     The non-limiting exemplary V(D)J protocol described below was employed to demonstrate the generation of sequencing libraries for both the 3′ and 5′ ends of mRNA targets of a targeted panel. 
     BD Rhapsody® Cell Capture and Reverse Transcription 
     1. Prepare single cell suspension of sample cells. 
     2. Follow standard BD Rhapsody® protocol for single cell capture through retrieval and bead wash and place beads on ice. 
     3. Make template switch reaction mix according to Table 1 below. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 TEMPLATE SWITCH REACTION MIX 
               
            
           
           
               
               
               
            
               
                   
                 200 uL 
                   
               
               
                 Reagent 
                 reaction 
                 Final concentration 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Water 
                 68 
                   
               
               
                   
               
               
                 5X SSIV buffer 
                 40 
                 1X 
               
               
                 (ThermoFisher) 
                   
                   
               
               
                   
               
               
                 dNTP (10 mM, 
                 20 
                 1 mM 
               
               
                 NEB N0447L) 
                   
                   
               
               
                   
               
               
                 0.1M DTT 
                 10 
                 5 mM 
               
               
                   
               
               
                 100 uM Template 
                 5 
                 2.5 uM 5′ TTT TTT TTT  
               
               
                 switch oligo (25 T) 
                   
                 TTT TTT TTT rG rG rG 3′ 
               
               
                   
                   
                 (SEQ ID NO: 50) 
               
               
                   
               
               
                 25 mM MgCl2 
                 24 
                 3 mM 
               
               
                   
               
               
                 20 mg/ml BSA 
                 1 
                 100 ng/ul 
               
               
                   
               
               
                 RNase inhibitor  
                 10 
                 2 U/ul 
               
               
                 (40 U/u1) 
                   
                   
               
               
                   
               
               
                 Ethylene glycol  
                 12 
                 66.8 ug/ul 
               
               
                 (1113.3 mg/ml) 
                   
                   
               
               
                   
               
               
                 SSIV (200 U/ul,  
                 10 
                 10 U/ul 
               
               
                 ThermoFisher) 
                   
                   
               
               
                   
               
               
                 Total 
                 200 
               
               
                   
               
            
           
         
       
     
     4. Place beads on magnet, remove supernatant and resuspend beads in 200 uL of the reaction mix. 
     5. Place tube on Thermomixer at 25 C for 30 min, followed by 1.5 h at 42° C., 1200 rpm. Place on ice after reaction finishes. 
     6. Place beads on magnet and remove supernatant. 
     7. Resuspend beads in 1 mL TE buffer. 
     8. Heat beads to 95° C. for 2 minutes to denature the mRNA. 
     9. Place beads on magnetic stand and remove supernatant. 
     10. Resuspend beads in 1 mL TE buffer. 
     11. Heat beads to 95° C. for 2 minutes to denature the mRNA. 
     12. Place beads on magnetic stand and remove supernatant. 
     13. Resuspend beads in 2 mL of pre-warmed (37C) HT1 buffer (Illumina, San Diego, Calif.). 
     Self-Hybridization 
     1. Shake tube for 5 min at 1200 rpm at 37° C. followed by 25 mins at 25° C. Place on ice afterwards. 
     2. Wash beads once with 1 mL HT1 buffer. 
     Klenow Extension 
     1. Prepare Klenow extension reaction mix shown in Table 2 below. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 KLENOW EXTENSION REACTION MIX 
               
            
           
           
               
               
               
            
               
                   
                 Reagent 
                 200 uL rxn 
               
               
                   
                   
               
               
                   
                 Water 
                 150 
               
               
                   
                 10× Klenow Buffer 
                  20 
               
               
                   
                 dNTP (10 mM) 
                  20 
               
               
                   
                 Klenow fragment exo-  
                  10 
               
               
                   
                 (NEB M0212S, 5 U/ul) 
               
               
                   
                   
               
            
           
         
       
     
     2. Place beads on magnetic stand and remove supernatant. 
     3. Resuspend beads in 200 uL of Klenow extension reaction mix. 
     4. Place in 37° C. thermomixer for 30 minutes, 1200 rpm. 
     5. Wash once with 1 mL TE. 
     Exol Treatment 
     1. Prepare Exol reaction mix according to Table 3 below. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 EXOI REACTION MIX 
               
            
           
           
               
               
               
               
            
               
                   
                 Component 
                 1 library (uL) 
                 1.2× 
               
               
                   
                   
               
               
                   
                 Water 
                 170.0 
                 204.0 
               
               
                   
                 10× exconuclease I buffer 
                  20.0 
                  24.0 
               
               
                   
                 Exonuclease I 
                  10.0 
                  12.0 
               
               
                   
                 Total 
                 200.0 
                 240.0 
               
               
                   
                   
               
            
           
         
       
     
     2. Place beads on magnet and remove supernatant. 
     3. Resuspend beads in 200 uL of Exol reaction mix. 
     4. Place tube in 37° C. thermomixer for 30 minutes, 1200 rpm. 
     5. Transfer tube to 80° C. thermomixer for 20 minutes, no shaking. 
     6. Place tube on ice for ˜1 minute. 
     7. Place beads on magnet. 
     8. Remove supernatant and resuspend beads in 200 uL of bead resuspension buffer. 
     PCRI Amplification 
     1. Prepare PCR1 master mix according to Table 4 below: 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 PCR1 MASTER MIX (TCR + IR + 5′IR + BCR) 
               
            
           
           
               
               
               
            
               
                 PCR1 
                 1× 
                 Final Concentration 
               
               
                   
               
            
           
           
               
               
               
            
               
                 PCR grade water 
                 3.4 
                   
               
               
                 Resolve PCR Mastermix (2× KAPA2G) 
                 100 
                 1× 
               
               
                 Immune response - Hs 
                 40 
                   
               
               
                 TCRa N1 primer - 10 uM 
                 1.2 
                 60 nM 
               
               
                 TCRb N1 primer - 10 uM 
                 1.2 
                 60 nM 
               
               
                 BCR pool N1 - 20 uM 
                 4.2 
                 60 nM 
               
               
                 5′ IR 30-plex - 20 uM 
                 18 
                 60 nM 
               
               
                 Universal Oligo (ILR2, 10 uM) 
                 20 
                  1 uM 
               
               
                 20 mg/ml BSA 
                 12 
                   
               
               
                 Total 
                 200 
               
               
                   
               
            
           
         
       
     
     2. (Optional) Subsample beads. 
     3. Place tube with beads on magnet and remove supernatant. 
     4. Resuspend beads in 200 uL of PCRI reaction mix. Pipetting gently to mix thoroughly. 
     5. Split evenly across (4) 0.2 ml PCR tubes (i.e. ˜50 ul±5 ul per tube). 
     6. In the Post-PCR room, run the following PCR protocol: 95° C. 3 min, 15 cycles of (95° C. 30 s, 60° C. 3 min, 72° C. 1 min), 72° C. 5 min. 4° C. hold. 
     7. After PCR, combine PCRI products and beads into a LoBind 1.5 ml microcentrifuge tube. 
     8. Place tube on 1.5 ml magnet and pipet PCRI products into a new tube. 
     PCR1 Cleanup 
     1. Add 200 ul Ampure XP beads (1× of the volume of PCR products) to PCR1 products. Mix well. 
     2. Incubate at room temperature for 5 min. 
     3. Prepare 80% ethanol fresh (e.g. 800 ul ethanol with 200 ul DNase/RNase-free water). 
     4. Place tubes with Ampure beads on 1.5 ml tube magnet for approximately 1-2 minutes. Remove supernatant after all beads are collected on the side of the tube. 
     5. Remove supernatant after all beads are collected on the side of the tube. 
     6. While tube is on magnet, add 500 ul 80% ethanol to wash bead pellet. 
     7. Remove as much ethanol as possible. 
     8. Repeat 80% ethanol wash once, for a total of 2 washes. 
     9. Let Ampure beads air dry on magnet with lid open until no obvious droplet is present (about 3-5 minutes. 
     10. While tube is on magnet, add 500 ul 80% ethanol to wash bead pellet. 
     11. Remove as much ethanol as possible. 
     12. Repeat 80% ethanol wash once, for a total of 2 washes. 
     13. Let Ampure beads air dry on magnet with lid open until no obvious droplet is present (about 3-5 minutes). 
     14. Resuspend Ampure beads in 30 ul Elution Buffer. 
     15. Place on 1.5 ml tube magnet. 
     16. Transfer supernatant to a new 1.5 ml tube. This is the purified PCR1 product. Store at 4° C. or on ice if doing the next step on the same day, or store at −20° C. until use. 
     PCR2 Amplification 
     1. In the pre-PCR area, prepare the following reaction mix: 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 TCR REACTION MIX 
               
            
           
           
               
               
               
            
               
                   
                 1× 
                 Final Concentration 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Resolve PCR MasterMix (2× KAPA2G) 
                 25 
                 1× 
               
               
                 TCRa N2 primer - 1 uM 
                 3 
                  60 nM each primer 
               
               
                 TCRb N2 primer - 1 uM 
                 3 
                   
               
               
                 Universal Oligo (ILR2, 10 uM) 
                 2 
                 400 nM 
               
               
                 PCR grade water 
                 12 
                   
               
               
                 Total 
                 45 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 BCR REACTION MIX 
               
            
           
           
               
               
               
            
               
                   
                 1× 
                 Final Concentration 
               
               
                   
               
               
                 Resolve PCR MasterMix (2× KAPA2G) 
                 25 
                 1× 
               
               
                 BCR N2 primer 20 uM 
                  1 
                  60 nM each primer 
               
               
                 Universal Oligo (ILR2, 10 uM) 
                  2 
                 400 nM 
               
               
                 PCR grade water 
                 22 
                   
               
               
                 Total 
                 45 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 13 
               
             
            
               
                   
               
               
                 IMMUNE RESPONSE 5′ PANEL 
               
            
           
           
               
               
               
            
               
                   
                 1× 
                 Final Concentration 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Resolve PCR MasterMix (2× KAPA2G) 
                 25 
                 1× 
               
               
                 5′ IR 30-plex - 20 uM 
                 4.5 
                  60 nM each primer 
               
               
                 Universal Oligo (ILR2, 10 uM) 
                 2 
                 400 nM 
               
               
                 PCR grade water 
                 13.5 
                   
               
               
                 Total 
                 45 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 14 
               
             
            
               
                   
               
               
                 IMMUNE RESPONSE 3′ PANEL 
               
            
           
           
               
               
               
            
               
                   
                 1× 
                 Final Concentration 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Immune response - Hs 
                 10 
                  60 nM each primer 
               
               
                 Universal Oligo (ILR2, 10 uM) 
                 2 
                 400 nM 
               
               
                 PCR grade water 
                 8 
                   
               
               
                 Total 
                 45 
               
               
                   
               
            
           
         
       
     
     2. Bring the reaction mix to the Post PCR area. 
     3. Add 5 ul cleaned up PCR1 products to 45 ul reaction mix. 
     4. Run the following PCR protocol in the thermal cycler in the post PCR area: 95° C. 3 min, 15 cycles of (95° C. 30 s, 60° C. 3 min, 72° C. 1 min), 72C 5 min. 
     PCR2 Cleanup 
     1. For TCR and BCR products, add 30 ul Ampure XP beads (0.6× of the volume of PCR products) to PCR1 products. For IR 3′ and 5′, add 50 ul Ampure XP beads (1× of the volume). Mix well. 
     2. Incubate at room temperature for 5 min. 
     3. Prepare 80% ethanol fresh (e.g. 800 ul ethanol with 200 ul DNase/RNase-free water). 
     4. Place tubes with Ampure beads on 1.5 ml tube magnet for approximately 1-2 minutes. Remove supernatant after all beads are collected on the side of the tube. 
     5. While tube is on magnet, add 200 ul 80% ethanol to wash bead pellet. 
     6. Remove as much ethanol as possible. 
     7. Repeat 80% ethanol wash once, for a total of 2 washes. 
     8. Let Ampure beads air dry on magnet with lid open until no obvious droplet is present. 
     9. Resuspend beads in 30 ul Elution Buffer. 
     10. Place on 1.5 ml tube magnet. 
     11. Transfer supernatant to a new 1.5 ml tube. This is the purified PCR2 product. Store at 4 C or on ice if doing the next step on the same day, or store at −20° C. until use 
     12. Measure amount of eluted DNA using Qubit DNA HS assay to evaluate if dilution of products is required for the next PCR. PCR2 products must be diluted to ≤10 ng/ul using Elution Buffer before proceeding to the Final PCR to avoid over-amplification. 
     Indexing PCR 
     1. In the pre-PCR area, prepare the following reaction mix shown in Table 9. 
     
       
         
           
               
             
               
                 TABLE 15 
               
             
            
               
                   
               
               
                 REACTION MIX 
               
            
           
           
               
               
               
               
            
               
                   
                 1× 
                 4.4× 
                 Final Concentration 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Resolve PCR Mastermix (2× KAPA2G) 
                 25 
                 110 
                 1× 
               
               
                 Resolve Library Forward Primer  
                 2 
                 8.8 
                 400 nM 
               
               
                 (P5, 10 uM) 
                   
                   
                   
               
               
                 Resolve Library Reverse Primer ** (P7, 
                 2 
                 8.8 
                 400 nM 
               
               
                 10 uM 
                   
                   
                   
               
               
                 PCR grade water 
                 18 
                 79.2 
                   
               
               
                 Total 
                 47 
                 — 
                   
               
               
                   
               
            
           
         
       
     
     2. Bring the reaction mix to the Post PCR area. 
     3. Add 3 ul cleaned up PCR2 products to 47 ul reaction mix. 
     4. Run the following PCR protocol in the post PCR area: 95° C. for 5 min, 8 cycles of (98° C. for 15 s, 60° C. for 30 s, 72° C. for 30 s), 72C for 1 min. 
     Final PCR Cleanup 
     1. Add 30 ul Ampure XP beads (0.6× of the volume of PCR products) to PCR products. Mix well. 
     2. Incubate at room temperature for 5 min. 
     3. Prepare 80% ethanol fresh (e.g. 800 ul ethanol with 200 ul DNase/RNase-free water). 
     4. Place tubes with Ampure beads on 1.5 ml tube magnet for approximately 1-2 minutes. Remove supernatant after all beads are collected on the side of the tube. 
     5. While tube is on magnet, add 200 ul 80% ethanol to wash bead pellet. 
     6. Remove as much ethanol as possible. 
     7. Repeat 80% ethanol wash once, for a total of 2 washes. 
     8. Let Ampure beads air dry on magnet with lid open until no obvious droplet is present. 
     9. Resuspend beads in 30 ul Elution Buffer. 
     10. Place on 1.5 ml tube magnet. 
     11. Transfer supernatant to a new 1.5 ml tube. This is the purified PCR2 product. Store at 4° C. or on ice if doing the next step on the same day, or store at −20° C. until use. 
     12. Measure amount of eluted DNA using Qubit DNA HS assay to evaluate if dilution of products is required for the next PCR. PCR2 products must be diluted to ≤10 ng/ul using Elution Buffer before proceeding to the Final PCR to avoid over-amplification. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 
     One skilled in the art will appreciate that, for this and other processes and methods disclosed herein, the functions performed in the processes and methods can be implemented in differing order. Furthermore, the outlined steps and operations are only provided as examples, and some of the steps and operations can be optional, combined into fewer steps and operations, or expanded into additional steps and operations without detracting from the essence of the disclosed embodiments. 
     With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. 
     It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” 
     In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group. 
     As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth. 
     From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.