Linkage disequilibria between HLA-B and the rarer properdin factor B alleles, BfF1 and BfS1.

Phenotypic association and highly significant linkage disequilibria have been demonstrated for HLA-B18 and BfF1 and HLA-Bw50 and BfS1 alleles among Caucasians from Australia and the United States (San Francisco Bay area). The HLA-B18, BfF1 association appears to be associated with HLA-Aw30. It is possible that BfS1 arose as a mutation, after the evolutionary splitting of HLA-Bw21, on an HLA-Bw50 haplotype, and that BfF1 arose on an HLA-Aw30, B18 haplotype.