A method for detecting antigen responsive T cells in a sample comprising: i) providing a composition comprising different subsets of multimeric MHCs, wherein each multimeric MHC comprises i) two or more given MHC-peptide molecules linked to a backbone molecule, and ii) at least one nucleic acid molecule linked to said backbone molecule, wherein said at least one nucleic acid molecule comprises a 5' first primer region, a central stretch of nucleic acids (barcode region) and a 3' second primer region, wherein said barcode region serves as a specific label for said two or more given MHC-peptide molecules; wherein each subset of multimeric MHC has a unique barcode region specific for the given MHC-peptide molecule; and ii) contacting said multimeric MHCs with said sample; and iii) removing unbound multimeric MHCs before amplification by washing and spinning; and iv) detecting binding of the multimeric MHCs to said antigen responsive T cells, thereby detecting T cells responsive to an antigen present in said multimeric MHCs, wherein said binding of said multimeric MHCs to said antigen responsive T cells is detected by a) amplifying by PCR the barcode region of said nucleic acid molecules linked to the cell-bound multimeric MHCs , and b) sequencing of said amplified barcode regions. i) providing a composition comprising different subsets of multimeric MHCs, wherein each multimeric MHC comprises i) two or more given MHC-peptide molecules linked to a backbone molecule, and ii) at least one nucleic acid molecule linked to said backbone molecule, wherein said at least one nucleic acid molecule comprises a 5' first primer region, a central stretch of nucleic acids (barcode region) and a 3' second primer region, wherein said barcode region serves as a specific label for said two or more given MHC-peptide molecules; wherein each subset of multimeric MHC has a unique barcode region specific for the given MHC-peptide molecule; and wherein each multimeric MHC comprises i) two or more given MHC-peptide molecules linked to a backbone molecule, and ii) at least one nucleic acid molecule linked to said backbone molecule, wherein said at least one nucleic acid molecule comprises a 5' first primer region, a central stretch of nucleic acids (barcode region) and a 3' second primer region, wherein said barcode region serves as a specific label for said two or more given MHC-peptide molecules; wherein each subset of multimeric MHC has a unique barcode region specific for the given MHC-peptide molecule; and ii) contacting said multimeric MHCs with said sample; and iii) removing unbound multimeric MHCs before amplification by washing and spinning; and iv) detecting binding of the multimeric MHCs to said antigen responsive T cells, thereby detecting T cells responsive to an antigen present in said multimeric MHCs, wherein said binding of said multimeric MHCs to said antigen responsive T cells is detected by a) amplifying by PCR the barcode region of said nucleic acid molecules linked to the cell-bound multimeric MHCs , and b) sequencing of said amplified barcode regions. a) amplifying by PCR the barcode region of said nucleic acid molecules linked to the cell-bound multimeric MHCs , and b) sequencing of said amplified barcode regions. <EOS>