PREDICTABILITY OF ALLOREACTIVITY AMONG UNRELATED INDIVIDUALS - ROLE FOR HLA-DPB1

compared the mixed lymphocyte culture reaction (MLR-I) among unrelated individuals who are carriers of the extended haplotype [HLA-B8,SC01,D R3,DRB10301,DQB1*0201] on one chromosome and the generic specificity HLA-DR4 on the second chromosome. Genomic DNA samples from the same in dividuals were also analyzed for HLA-DRB1, DQB1 and DPB1 alleles by PC R and SSOPH typing and for DOB polymorphism by RFLP. HLA-DRB1 alleles, in paired MLR responses between unrelated individuals indicated that matching of HLA-DRB1 was a better predictor of non-reactivity than ide ntity in HLA-DR generic types, (43% vs 22%). Moreover, 90% of the DRB1 matched pairs had nonreactive and weakly reactive MLR, whereas only 3 7% of DRB1 mismatched unrelated individuals gave weak or no reactions. Matching for HLA-DRB1 and HLA-DPB1 alleles eliminates a significant n umber of cell mixtures with MLR-I reactivity. Furthermore, some DPB1 m ismatches, but not all, do not seem to elicit MLR-I reactivity.