Different functions and associations of HLA-DR and HLA-DQ(DC) antigens shown by serological, cellular and DNA assays.

Two consanguineous Caucasoid HTCs, DHI and FPA, were investigated, the latter having an unusual HLA-DR/DQ(DC) association. Both these HTCs typed clearly as HLA-DRw11. However, while DHI typed as DRw11/DQw3(DC4) as expected, FPA typed as DRw11/DQw1(DC1) instead. Although extremely rare in Caucasoids, DRw11/DQw1 is a common pattern of association in Nigerian Negroids. Southern blots of DNA extracted from EBV cell line derived from FPA, hybridized with HLA-DC alpha and HLA-DC beta probes, confirmed this unusual DRw11/DQw1(DC1) association. In addition the DC alpha probe showed a unique additional restriction fragment length polymorphism (8 kb) attributable to the DX gene in the FPA DNA. When DHI and FPA were used as stimulators in MLC, the patterns to typing responses obtained were not completely concordant although they overlap to some extent. For this reason FPA has been locally designated Dw'F5', distinct from Dw5. Furthermore, the HLA-DQ antigens of the responder cells were not necessarily the same as those of the HTCS to which they gave typing responses (FPA and DHI). Functional studies using these two HTCs showed that the DQ(DC) antigens probably have no direct lymphocyte activating properties but rather have a regulatory role in controlling responses to allodeterminants in MLC.