HLA-DR antigens in Black North-Americans and their association with HLA-D.

A random population of 108 Black North-Americans, 79 of whom had also been typed for HLA-D in Mixed Leukocyte Culture (MLC), were serologically tested for DRw with Seventh International Histocompatibility Workshop trays. Clusters of B cell alloantisera were identified which defined several DRw antigens. Although the clusters for DRw1, DRw2, DRw3 and DRw7 showed similarities with the clusters derived during the Seventh International Histocompatibility Workshop, distinct differences were observed which should be taken into account for the assignment of the DRw antigens in Blacks. DRw6 was defined by a cluster of sera which also reacted with DRw1 and DRw2 cells. The tails of these sera were used to assign DRw6, but this was only possible with DRw1 and DRw2 negative cells. It was not possible to identify serum clusters specific for DRw4 or WIA8. The associations between DRw and the corresponding Dw specificities were reasonably good for DRw1, DRw2 and DRw7, but weaker for DRw3 and DRw5. The cumulative gene frequencies for DRw1, DRw2, DRw3, DRw5, DRw6 and DRw7 was 0.86. The frequencies of these six DRw antigens fitted into a Hardy-Weinberg distribution, suggesting that DRw in Blacks is controlled by a single gene with multiple alleles.