Genetic polymorphism of the seventh component of complement: a new variant.

Genetic polymorphism of the seventh component of complement (C7) was studied by the methods of agarose gel isoelectric focusing and immunoblotting. Serum or plasma samples were treated with neuraminidase prior to isoelectric focusing. A cathodal variant, named C7 5, was recognized in the treated samples. Family study indicates that the C7 5 component is genetically determined. The allele frequencies calculated from 183 healthy Japanese individuals were C7*1 = 0.809, C7*2 = 0.104, C7*4 = 0.038, and C7*5 = 0.049. An association between C7 and C6 alleles was not found.