Less active on cholesterol-containing membranes. This killing is inactivated by heating at 56C fo 30 min. This is due to complement. Opsonic Chemotactic Lytic. Contains 25 separate activation and regulatory molecules and at least seven receptors.
Nomenclature makes it difficult to follow.
Human IgM and some forms of IgG activate C1. Activated C1s is a protease that sequentially cleaves additional molecules in the cascade specifically C4 then C2, whose products combine to form a complex protease, C14b2a, or C3 convertase. Enzymatic cleavage of C3 by either pathway generates C3b and the small anaphylatoxic C3a. C3 cleavage results in exposure and activation of an internal thioester group in C3b that can form form a covalent ester bond with hydroxy groups, or form a covalent amide bond with amino groups. Diverse microbial compounds can activate ranging from LPS to Teichoic acids. Because a similar pathway is found in some invertebrates, it probably preceded adaptive immunity attributable to B-cells and antibody.