Cloned primed lymphocyte test cells recognize the fourth, fifth, and sixth hypervariable regions at amino acid positions 65-87 of the DPB1 molecule.

Genetic polymorphisms of the HLA-DPB1 gene in Japanese and Caucasian panel cells defined by PLT were analyzed by the PCR-based genotyping technique PCR-RFLP, and suballeles of DPw3 (DPB103) and DP"Cp63" (DPB109) could be detected. PLT-defined DPw3 cells were typed by PCR-RFLP as either DPB10301 or DPB11401. On the other hand, PLT-defined DPCp63-typed cells were typed as DPB10901 or DPB11001. These results indicate that both DPw3 and DPCp63 are split into two subantigens. DPw2 and DPw4 are DPB10201 and 0202 and DPB10401 and 0402, respectively. Comparative analysis of the amino acid sequences of the DPw2-, DPw4-, DPw3-, and DPCp63-associated alleles revealed that the fourth (C), fifth (D), and sixth (E) hypervariable regions at amino acid positions 65-87 were shared within the same PLT-defined DP antigen groups, suggesting that these three hypervariable regions are recognized by cloned T cells in PLT, thus determining DP antigen specificity. On the basis of this model, 44 DPB1 alleles can be classified into 18 antigen groups, each of which may possibly represent a PLT-defined single DP specificity.