Mapping of the HLA locus controlling C2 structural variants and linkage disequilibrium between alleles C2 2 and Bw15

The newly discovered polymorphism of human C2 protein analyzed by isoelectric focusing is controlled by a locus closely linked to HLA. An informative cross‐over family (HLA: A×C) indicates that this locus maps on the C side of the region. Population and family studies have shown that the C2 2 variant is significantly associated on the haplotype with alleles Bw15 and Cw3. The fact that the “deficient” C2 mutant is in linkage disequilibrium with other HLA antigens, suggests that C2 2 and C2 0 , here tentatively considered alleles of the same locus, are not directly related by descent.