Recombination between DQ alpha and DQ beta genes generates human histocompatibility leukocyte antigen class II haplotype diversity.

Two major DR7 haplotypes have been defined on the basis of serologic typing: those that type as DQw2 and others that type as DQw3. In order to define the molecular basis for these serologic differences we have isolated and sequenced DQ alpha, DR beta I, and DQ beta cDNA clones from both representative haplotypes. These studies reveal that although the DQ alpha and DR beta I genes of both haplotypes are identical, the DQ beta genes are very different. These data suggest that the serologic differences of these two DR7 haplotypes are the result of a recombinational event that occurred between the DQ alpha and DQ beta genes. In addition, they emphasize the role of DQ recombination in generating "hybrid" HLA-DQ heterodimers.