C4 polymorphism and HLA linkage: Studies in a family with hereditary C4 deficiency

Abstract Family studies of C4 polymorphism and HLA linkage are presented. The proband had a lupus-like syndrome and the complete absence of hemolytic and immunochemical C4. Eleven family members covering three generations with reduced serum C4 levels had the MHC haplotype A26, Bw49, DR2, BFS, C2C, GLO-2. C4 polymorphism studies showed that the proposita was homozygous for a doubly deficient C4 haplotype, C4A ∗ QO,C4B ∗ QO and that in the family the C4 loci, C4A and C4B, were closely linked to HLA.