Molecular complexity of HLA-DQw3: the TA10 determinant is located on a subset of DQw3 beta chains.

In attempts to examine the relationships between serologic and structural polymorphisms of HLA-DQ molecules we have analyzed several monoclonal antibodies generated against polymorphic determinants on HLA-DQ molecules. One antibody, SFR20-DQw3, has a serologic reactivity like that of the previously characterized anti-DQw3-like monoclonal antibody, IVD12, but differs from IVD12 in its affinity for DQw3 molecules associated with DR4 and DRw9 haplotypes. Two other monoclonal antibodies have identical serologic and molecular specificity, and react with a subset of DQw3 positive cells; they have been designated SFR20-DQ beta 5. Biochemical analysis of the DQ molecules carried by DQw3-positive cell lines associated with different DR haplotypes (DR4, DR5, DRw8, DRw9, DRw12), reveal the presence of at least three different kinds of beta chains carrying the DQw3 epitope. All the cell lines bound by SFR20-DQ beta 5 (DR5, DRw8, and DRw12) possess DQ beta chains of indistinguishable electrophoretic mobility, which are different from the DQ beta chains of DQw3 cell lines not bound by this antibody while DQw3 beta chains carried by DR4 and DRw9 haplotypes are distinct from DQ beta 5-positive BLCL and from each other. The serologic reactivity of antibody DQ beta 5 correlates perfectly with an RFLP of the DQ beta gene designated DQw3.1 (Kim et al.: PNAS 828139, 1985), and with the serologic specificity TA10 as defined during the Ninth International Workshop (Schreuder GMT et al.: Histocompatibility Testing 1984). SFR20-DQ beta 5 reacts with a separated beta chain by Western blot analysis. The finding of indistinguishable beta chain electrophoretic mobility for all DQ beta 5/TA10 positive cell lines tested provide the molecular basis for these specificities, and strongly suggest that antibody SFR26-DQ beta 5 detects a single allele of the multiple DQ beta alleles which can contribute to the formation of the DQw3 specificity.