Failure of rat and rabbit antiserum to passively sensitize normal and pertussis-treated rats and mice so as to induce mast cell damage and histamine release on later contact with antigen.

It was observed that passive anaphylaxis in rats and mice is not accompanied by mast cell damage or histamine release and does not duplicate the full picture of active anaphylaxis in these species. Furthermore, pretreatment with although enhancing mast cell damage and histamine release in active anaphylaxis of rats and mice does not induce these phenomena in passive anaphylaxis. It was also observed that injection of soluble antigen-antibody complexes in rats and mice also do not reproduce the mast cell damage and histamine release found in active anaphylaxis. It is suggested that the mast cell damage and histamine release in active anaphylaxis of rats and mice is due to non-precipitating antibodies of an unknown nature and that anaphylaxis in passively sensitized rats and mice is the consequence of interaction of antigen with precipitating antibodies which do not lead to mast cell damage or histamine release in these species. It is also suggested that in active sensitization of rats and mice acts by stimulating the production of antibodies that are very efficient in inducing mast cell lysis on reaction with antigen. The possible role of soluble antigen-antibody complexes in passive anaphylaxis of these species is considered.