EXTENDED HLA-DQw2 HAPLOTYPES: MOLECULAR ANALYSIS

SUMMARY The HLA‐DQw2 specificity, homogeneous in serology, is strongly associated to two HLA‐DR specificities: DR3 and DR7. These alleles are found mainly on DQw2 bearing extended haplotypes with strong linkage disequilibrium. We describe, with BamHI, HindIII and RsaI, two restriction fragments length polymorphisms (RFLP) for the A gene of DQw2. These two subtypes correlated with the DR3 and DR7 specificities. Interestingly, by non‐equilibrium pH gradient electrophoresis (NEPHGE), two DQα chains were also found, respectively correlated with the same DR specificities. In addition, Hindi polymorphism allowed us to distinguish several patterns of B genes for (DR7) DQw2 haplotypes but without any detectable association with another HLA marker. However, only one DQ(3 chain was found by NEPHGE in the (DR7) DQw2 haplotype. Furthermore, MncII discriminated the B genes of the two extended haplotypes: (B8, DR3) DQw2 and (B18, DR3) DQw2. The same result was found by NEPHGE: two DQβ chains were described, corresponding to the same extended haplotypes. The use of exon‐specific DQB probes showed that the genomic polymorphism in DOw2 haplotypes is located, at least, at the 3’end of the gene. These data add new characteristics to the different DQw2 extended haplotypes.