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Abstract A second anticomplementary material in cobra venom is described and characterized by its large molecular size (0.8 to 1.0 × 106 molecular weight), its action on the early components of complement, but not C3 or C5, and its inability to lyse guinea pig erythrocytes. The low molecular weight cobra factor (140,000) has both anticomplementary activity and guinea pig erythrocyte hemolytic activity in vitro. Its ability to lyse erythrocytes depends on the formation of a complex between L-CoF and a cofactor in serum and upon an intact sequence of complement components from C3 on. Purified L-CoF was found to bind to the surface of guinea pig erythrocytes in very small amounts so that lysis of the cells occurred after washing and exposure to a source of C3–C9. Mechanisms for the hemolysis of guinea pig erythrocytes by cobra factor are discussed.
Ballow et al. (Sat,) studied this question.