Genetic polymorphism of human complement component C81 in the Japanese population.

Genetic polymorphism of human C81 has been investigated using polyacrylamide gel isoelectric focusing (PAGIEF) in the presence of 3.1 M urea followed by electroblotting with enzyme immunoassay. In 448 individuals phenotypes of C81 were classified into three common and four rare patterns, and these were considered to be controlled by two common alleles, C81 A and C81 B, and three rare alleles which were tentatively designated C81 A1J and C81 A2J for acidic variants and C81 B1J for the basic variant. The alleles of C81 A2J and C81 B1J are new rare alleles, but C81 A1J might correspond to C81 A1 in the former studies. Family data were in accordance with the hereditary rules. The gene frequencies were estimated as C81 A is 0.6228, C81 B is 0.3672, C81 A1J is 0.0078, C81 A2J is 0.0011, and C81 B1J is 0.0011, respectively. The gene frequencies of the two common alleles agreed approximately with other ethnic groups. PAGIEF of neuraminidase-treated plasma samples followed by electroblotting with enzyme immunoassay is applicable to the study of heterogeneity of C81.