HLA class II DP epitopes.

Both alpha (DPA1) and beta (DPB1) peptide chains of class II HLA-DP heterodimers contain polymorphic regions. Five DPB1 epitopes, for which we propose numbers #4001-4005, were identified by the reaction patterns ofthe DPB1 antibodies to DPB1 alleles of DP single antigen beads. Epitopes were defined by unique amino acids shared by the positive antigens of theantibodies. The unique amino acids for #4001 are DEAV at positions 84-87; for #4002, they are DED at positions 55-57; for #4003, DEE at positions 55-57; for #4004, Q at position 33; for #4005, the unique amino acids may be GGPM at positions 84-87. An antibody to epitope #4001-shared by DPB1*01, 03, 05, 09, 10, 11, 13, 14, 17, 19- could be absorbed by the cell line of DPB1*01 typing. This eluted antibody was reactive to all the DPB1 #4001 specificities. So this test demonstrated that a single antibody was reactive to the epitope shared by multiple antigens.