Complement-dependent anaphylactic reactions.

The concept of elicitation of reactions of anaphylactic type by non-tissue-fixing antibody, through activation of complement and release of anaphylatoxins by antigen-antibody complexes in vivo, is not clearly defined by published evidence. Experimental data are presented to demonstrate that guinea pig immunoglobulin G2 (noncytotropic) complexed with antigen in vitro elicits dermal reactions in guinea pigs, and that pretreatment of animals with complement-inactivating cobra venom factor diminishes such reactions. The various pathways through which immediate hypersensitive reactions may occur are discussed.