A method for developing a therapeutic, comprising: (a) expressing an affinity acceptor tagged HLA protein in human cells, wherein the affinity acceptor tagged HLA protein is a class II HLA protein that comprises a sequence encoded by an HLA class II allele expressed by a human subject, wherein the affinity acceptor tagged HLA class II protein is encoded by a recombinant polynucleic acid comprising: (i) a sequence encoding the HLA class II allele expressed by the human subject linked to, (ii) a sequence encoding an affinity acceptor peptide, thereby forming affinity acceptor tagged class II HLA-peptide complexes that are expressed by the human cells; wherein the affinity acceptor tagged HLA-peptide complexes incorporate into a cell membrane when expressed; (b) identifying a class II HLA-allele specific peptide or complex of the affinity acceptor tagged class II HLA-peptide complexes; and (c) developing a therapeutic based on one or more sequences of a class II HLA-allele specific peptide or complex identified, wherein the therapeutic comprises: (i) one or more peptides comprising the one or more sequences, (ii) a polynucleotide encoding the one or more peptides comprising the one or more sequences, (iii) one or more APCs comprising the one or more peptides comprising the one or more sequences, (iv) a T cell receptor (TCR) specific for an HLA in complex with the one or more peptides comprising the one or more sequences, or (v) a cell comprising a TCR or a chimeric T cell receptor (CAR) specific for an HLA in complex with the one or more peptides comprising the one or more sequences. (a) expressing an affinity acceptor tagged HLA protein in human cells, wherein the affinity acceptor tagged HLA protein is a class II HLA protein that comprises a sequence encoded by an HLA class II allele expressed by a human subject, wherein the affinity acceptor tagged HLA class II protein is encoded by a recombinant polynucleic acid comprising: (i) a sequence encoding the HLA class II allele expressed by the human subject linked to, (ii) a sequence encoding an affinity acceptor peptide, thereby forming affinity acceptor tagged class II HLA-peptide complexes that are expressed by the human cells; wherein the affinity acceptor tagged HLA-peptide complexes incorporate into a cell membrane when expressed; (i) a sequence encoding the HLA class II allele expressed by the human subject linked to, (ii) a sequence encoding an affinity acceptor peptide, (b) identifying a class II HLA-allele specific peptide or complex of the affinity acceptor tagged class II HLA-peptide complexes; and (c) developing a therapeutic based on one or more sequences of a class II HLA-allele specific peptide or complex identified, wherein the therapeutic comprises: (i) one or more peptides comprising the one or more sequences, (ii) a polynucleotide encoding the one or more peptides comprising the one or more sequences, (iii) one or more APCs comprising the one or more peptides comprising the one or more sequences, (iv) a T cell receptor (TCR) specific for an HLA in complex with the one or more peptides comprising the one or more sequences, or (v) a cell comprising a TCR or a chimeric T cell receptor (CAR) specific for an HLA in complex with the one or more peptides comprising the one or more sequences. <EOS>