C4 allotyping distinguishes HLA-B14.1 and B14.2 subgroups.

Complement allotyping (C4, C2, and BF) was performed in 60 unrelated individuals and 15 families characterized for the subtypes (14.1 and 14.2) within HLA-B14. Eighty-seven percent of B14.2 individuals typed positive for the rare C4A2 variant. In contrast, less than 7% of B14.1 individuals were positive for this C4 allotype which is in keeping with a control background frequency. Family studies revealed that three distinct complotypes (complement haplotypes) are characteristic for the two HLA-B14 subgroups. The SC22 and FC31 complotypes characterize the B14.2 subtype, whereas SC31 appears to define B14.1.