Genetic control of the eighth component of complement.

Using isoelectric focusing in polyacrylamide gel and a hemolytic assay for development of patterns, extensive, structural polymorphism in human C8 has been delineated. Two alleles, C8A and C8B, have been identified in orientals, with gene frequencies of 0.655 and 0.

Inherited deficiency of the sixth component of complement: a silent or null gene.

Four families have been studied, some members of which have inherited deficiency of the sixth component of complement. The genetically determined electrophoretic variants of C6 were evaluated in all family members. Seven individuals were found who did not have the variant found in the serum of the parent from whom they inherited the deficiency.

Cobra venom factor: evidence for its being altered cobra C3 (the third component of complement).

Evidence is presented that cobra venom factor, the anticomplementary protein in Naja naja venom, is modified cobra C3 (the third component of complement). Antiserum to the cobra venom factor cross reacts with human C3. A protein in cobra serum reacts strongly with antiserum to the venom factor and the former protein, like human C3, is converted by incubation of cobra serum with endotoxin, hydrazine, or simple storage at 37 degrees C.