The complement system of carp Cyprinus carpio-IV. Formation and characteristics of an intermediate complex EAC1,4,2 in immune hemolysis by carp complement.

Abstract

A hemolytic intermediate complex EAC1, 4, 2 was prepared by incubating carp EAC1, 4 with hydrazine-treated carp serum, which is deficient in C4 and C3, at 0°C for 20 min. The difference between EAC1, 4, 2 and EAC1, 4 was shown by tests with inactivated carp sera. The former was hemolyzed by carrageenan-treated serum (Cn), ammonia-treated serum (Am) and heat-treated serum (H), whereas the latter was hemolyzed by Cn and Am, but not by H. EAC1, 4, 2 was unstable. Its half-life was about 15 min at 20°C and about 2.5h at 0°C. Addition of Ca2+ to the buffer was not effective in preventing the deterioration of this complex. The reaction between EAC1, 4 and Cy' (a mixture of complement components other than C1 and C4) proceeded only in the presence of Mg2+, whereas the reaction of EAC1, 4, 2 with Cy'proceeded without Mg2+. This indicates that the action of C2 requires Mg2+ while C3 acts without Mg2+.