HLA haplotypes with C4B5; evidence for further allelic heterogeneity.

Twenty-three individuals from various disease groups and normal controls were identified by immunofixation with anti-C4, C4-dependent lysis, determination of Rg (Rodgers) and Ch (Chido) phenotypes, and immunoblotting with C4-specific mouse monoclonal antibody. We found that one haplotype predominates with the C4B*5 allele, HLA-A11, B22(55), Cw3, Bf*S, C4A*4B*5, which also carries the Ch1,-2, 3 haplotype. The B5 allotype was also found with HLA-B60, HLA-B35 in Caucasoids, and HLA-B18 in non-Caucasoids; these carried the Ch-1, -2, -3 haplotype. Our results are in accord with an earlier report of two B5 subtypes, B5Rg+ and B5Rg- (Roos et al. 1984). The specificity of the mouse monoclonal antibodies IC4 and 2B12 had been previously related to C4A and C4B, respectively, but our results suggest that they relate more closely to Rg and Ch determinants.