Structural heterogeneity of C2 Complement protein and its genetic variants in man: a new polymorphism of the HLA region.

Abstract

A zymogram method, following thin-layer isoelectric focusing in a polyacrylamide gel, allows resolution of the lytic activity of serum C2 complement protein in a spectrum of molecular forms. This spectrum is characteristic in each of the species studied (man, rhesus monkey, guinea pig and hamster). Two different alternative patterns are observed in man: each of the 6 major lytic bands characteristic of the most common pattern (herein designated C21) is duplicated in the least common pattern (C22-1), with an additional band displaced cathodally by not more than 0.04 pH unit. Distribution of phenotypes C21 and C22-1 in a Caucasion population is in agreement with the hypothesis that they are controlled by 2 alleles, C21 and C22, with frequencies 0.96 and 0.04 .+-. 0.01. Segregation studies show that the 2 alleles are codominant and identify a locus in the HLA region. No recombinants with HLA-B were detected among 27 informative meioses, generating a cumulative lod score of 6.321. The individuals with the C2-deficient trait might be interpreted as homozygotes for a 3rd and rarest amorph C20 of the same locus.