HLA A*, B*-BF* and C4 A*, B* allele associations, with special reference to BF*S07, in the Tunisian population.

The HLA A2, Bw50-BFS07-C4 A2, B1 linkage group was transmitted unambiguously in four unrelated Tunisian families. In one of these, another allele association, also carrying BFS07, HLA A9, Bw50-BFS07-C4 A1, B1, was encountered. The previously reported linkage disequilibrium between BFS07 and HLA Bw50, a subtypic specificity of HLA Bw21, is confirmed in our study. The C4 A2, B1 haplotype, rare in the other populations until now studied, seems more frequent in Tunisia since it has been also found linked to HLA A11, B27 and BFS in one of these families. Other allele associations were unambiguously demonstrated with predominantly the C4 A3, B1 haplotype, particularly a rare HLA A3, B18-BFF1-C4 A3, B1 linkage group. A silent gene at the C4 A locus was found linked to HLA B*8.