Complement: Increased Efficiency of the Second Component after Treatment with Iodoacetamide

The apparent activity of the second component of human complement was enhanced by treatment of the purified protein with iodoacetamide. By contrast, treatment with iodoacetic acid or p-chloromercuribenzoate led to inactivation. Treatment with iodoacetamide prevented the effect of p-chloromercuribenzoate and vice versa. Enhanced activity was partly due to increased stability of the otherwise labile intermediate complex consisting of erythrocytes, antibody, and the first, second, and fourth components of complement.