Immunochemical Quantitation of the Third, Fourth and Fifth Components of Human Complement: Concentrations in the Serum of Healthy Adults,

Summary Immunochemical quantitation of the third, fourth and fifth components of human complement is feasible with the single radial immuno-diffusion technique. Serum component concentrations (mg/ml) in 25 healthy adults were: C′3, 1.23 ± 0.26 (0.86 to 1.84); C′4, 0.436 ± 0.118 (0.240 to 0.800) and C′5, 0.076 ± 0.024 (0.042 to 0.140). The experimental error of the quantitation was 10% for C′3 and C′4 and 15% for C′5. The immunochemical quantitation is influenced by in vitro conditions which allow physicochemical alterations in complement proteins; inclusion of ethylenediaminetetraacetate in the agar and the use of fresh serum or serum stored at -70°C circumvents this problem.