Genetics of complement C4. Two homoduplication haplotypes C4S C4S and C4F C4F in a family

Abstract
A family in which two homoduplicated C4 haplotypes (or supergenes) segregate is described. One haplotype C4F * 3 C4F *2.2 is composed of two C4F alleles and the other C4S * 5.1 C4S *1 of two C4S alleles. The C4F duplication haplotype is a partial inhibitor of the Rodgers antigen, and judged from our family and population material, it seems to be rather frequent and associated with HLAB *35, Bf * F, and HLAD/DR *1. The C4S duplication haplotype is Rg(a-) and is not identified in individuals without another S, Ch(a+) variant.