Restriction fragment length polymorphism of HLA-DRw53 detected in South African blacks and individuals of mixed ancestry.

The HLA-DRw53 specificity has not until now been shown to demonstrate polymorphism. We have studied 33 DRw53 haplotypes, comprising 19 DR4, 10 DR7, and 4 DR9 haplotypes, from 6 homozygous typing cells, 11 families, and 8 random individuals. All the subjects studied were South African blacks or of mixed ancestry (Cape Coloureds), with the exception of four homozygous typing cells from whites. The DNA was digested with TaqI and, after Southern blotting, was hybridized with a full-length DRB cDNA probe. Fragments correlating with DR4 (5.5 kb), DR7 (4.0 kb), and DR9 (4.1 kb) were observed. Two fragments of 14.5 and 2.8 kb correlated with DRw53. In addition, two pairs of fragments demonstrated a diallelic pattern, which is likely to correlate with a polymorphism of the DRB4 (DRw53) gene, since one or other of the two patterns was observed in all cells carrying the DRw53 specificity. The first allelic pattern, called DRw53a, was characterized by the presence of 7.5- and 2.6-kb fragments, while the second pattern, called DRw53b, had 5.8- and 2.7-kb fragments. DRw53a occurred in 10 of the 19 DR4 haplotypes and 7 of the 10 DR7 haplotypes. All three DR9,DQw2 haplotypes were also associated with DRw53a. These findings may have important implications for disease associations and the use of unrelated donors for organ transplantation.