C4 polymorphism and extended HLA haplotypes in Namibian San and Khoi and in South African Xhosa

We studied C4A and C4B polymorphisms and HLA‐B and ‐DR associations in the San, Khoi and Xhosa. C4A and C4B alleles were determined using conventional protein allotyping methods. The C4A*3, C4B*1 haplotype had a high frequency (30–55%) in all populations. The frequency of C4A*3, C4B*Q0 was 7–19%. The C4A*Q0, C4B*1 haplotype was frequent (15%) in the Khoi but very rare in the San (P0.001). C4A*12 A*91, C4B*Q0 was frequent in the Xhosa (15%) but rare in the San and Khoi (P0.001). Alleles C4A*5 and C4A*6, and the C4B*2 B*92 duplication were only found in the Xhosa. C4A alleles A*4, A*45, A*58, A*12, A*14, A*19 and the C4A*3 A*91 duplication were only found in the San/Khoi population group. In the San, fourteen extended haplotypes were found in a relatively high frequency (2–7%). In the Xhosa, one extended haplotype (B42, C4A*12 A*91, C4B*Q0, DR18) was found in a very high frequency (13%) and was characteristic for this group; five other extended haplotypes were found with a low frequency (3%).