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 co nventional protein allotyping methods. The C4A3, C4B*1 haplotype had a high frequency (30-55%) in all populations. The frequency of C4A3, C4BQ0 was 7-19%. The C4A*Q0, C4B*1 haplotype was frequent (15%) in th e Khoi but very rare in the San (P<0.001). C4A12 A*91, C4B*Q0 was fre quent in the Xhosa (15%) but rare in the San and Khoi (P<0.001). Allel es C4A5 and C4A*6, and the C4B*2 B*92 duplication were only found in the Xhosa. C4A alleles A4, A*45, A*58, A*12, A*14, A*19 and the C4A*3 A91 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, C4A12 A 91, C4B*Q0, DR18) was found in a very high frequency (13%) and was ch aracteristic for this group; five other extended haplotypes were found with a low frequency (<3%).