Genetic studies of low-abundance human plasma proteins. IX. A new allele at the complement subcomponent C1R structural locus.

Genetic variation in the C1R subcomponent of the first complement component C1 was investigated in U.S. whites by isoelectric focusing and immunoblotting. In addition to the previously described two alleles, the products of a new and rare third allele designated C1R3 were detected. The expression of the new allele is consistent with autosomal codominant inheritance, which is confirmed by family data. The frequencies of the C1R1, C1R2 and C1R3 alleles in 201 randomly selected U.S. whites are: 0.908, 0.090, and 0.002, respectively.