Polymorphism of the Second Component of Human Complement (C2)

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Abstract
The polymorphism of the 2nd component of human complement [C2] was studied by isoelectric focusing in polyacrylamide gels with subsequent complement-dependent lysis of sensitized sheep erythrocytes in an agarose overlay containing C2-deficient or normal human serum. In a material of 289 unrelated individuals the following gene frequencies were observed: C21 = 0.965 and C22 = 0.035. The rare phenotype C2 2 (= C2 B) was seen once in a child of a C2 1-2 heterozygous mother. The investigation of the C2/HLA relationship revealed a very close linkage. Among 62 informative meiotic divisions 1 recombination between HLA-B and C2 was found (i.e., 1.61%); in addition, C22 was significantly associated with HLA-B15 and HLA-Cw3. In a family with an HLA-A/C crossover C2 segregated together with HLA-C, in a family with an HLA-B/D(DR) crossover C2 segregated together with HLA-D(DR). The assumption that the C2 structural locus is located outside HLA-B, probably near HLA-D(DR), is supported.
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