Family study on the polymorphisms of the sixth and seventh components (C6 and C7) of human complement: linkage and haplotype analyses.

Genetic polymorphisms of the sixth and seventh complement components (C6 and C7) have been studied in Japanese family material using polyacrylamide gel isoelectric focusing followed by immunoblotting. Three common and four rare alleles were observed at the locus for C6. Inheritance of the two rare C6 variants, M11 and B3, was first confirmed. Three common C7 allotypes were classified as C7 1, C7 2, and C7 4, respectively. Linkage analysis confirmed the close linkage between the loci for C6 and C7. The maximum lod score was 8.43 at phi = 0 (95% confidence limits: phi = 0 and phi = .07). No significant linkage disequilibrium was found between C6 and C7 in directly determined haplotypes of unrelated parents.