ANTIGEN-INDUCED RELEASE OF SLOW REACTING SUBSTANCE OF ANAPHYLAXIS (SRS-A(RAT)) IN RATS PREPARED WITH HOMOLOGOUS ANTIBODY

The polymorphonuclear leukocyte appears to be an essential cellular prerequisite for the antigen-induced release of SRS-A(rat) in the peritoneal cavity of rats prepared with homologous, hyperimmune antisera. Depletion of PMN leukocytes is associated with a marked suppression of SRS-A(rat) release, whereas depletion of circulating lymphocytes or peritoneal mast cells does not influence the antigen-induced release of SRS-A(rat). A local increase in the number of PMN leukocytes produced by the induction of a peritoneal exudate was associated with an enhanced release of SRS-A(rat). A distinct difference in the cellular requirements for the antigen-induced release of histamine and SRS-A(rat) in the rat was observed. Homocytotropic antibody-mediated histamine release could be achieved in leukopenic rats but not in mast cell-depleted animals. Conversely, SRS-A(rat) release was suppressed in leukopenic rats but was unaffected by mast cell depletion. Diethylcarbamazine inhibited the antigen-induced release of SRS-A(rat) following preparation with homologous, hyperimmune antisera but did not interfere with homocytotropic antibody-mediated histamine release. In preventing SRS-A(rat) release, diethylcarbamazine did not interfere with antigen-antibody interaction since desensitization of tissues was possible in the presence of this inhibitor. This observation is consistent with the view that diethylcarbamazine inhibits the reaction sequence leading to the formation and release of SRS-A(rat) at some step subsequent to antigen-antibody interaction. These studies support the view that the immunologic pathways leading to the release of SRS-A(rat) and histamine in the rat are distinctly different in terms of the immunoglobulins involved, the cellular prerequisites, and the effective pharmacologic inhibitors.