Genetic polymorphism of the seventh component of complement in a Japanese population.

Genetic polymorphism of C7 in a Japanese population has been described, using polyacrylamide gel isoelectric focusing electrophoresis followed by an electrophoretic blotting technique. Phenotypes of C7 were classified into six common patterns, and observed phenotypes were produced by autosomal codominant at a single locus with three alleles. Three common alleles, designated C7*B, C7*M and C7*A, were found, and gene frequencies calculated from 494 individuals showed C7*B = 0.858, C7*M = 0.096 and C7*A = 0.046, respectively. It is noteworthy that both C7*M and C7*A have polymorphic frequencies in the Japanese population. The distribution of phenotypes fitted the Hardy-Weinberg equilibrium. Results indicate that the electrophoretic blotting technique, which has high specificity and sensitivity, is applicable in the study of heterogeneity of protein antigens.