Influence of mouse genotype on passive systemic anaphylaxis by immune complexes.

The influence of mouse genotype on passive systemic anaphylaxis (PSA) by immune complexes was studied. PSA was induced by using Brucella abortus endotoxin as the antigen and rabbit anti-Brucella endotoxin antisera. Experiments using syngeneic mice as well as mice congenic for H-2 showed that the H-2 haplotype influenced the sensitivity of mice to PSA. Among the H-2 haplotypes studied, H-2b was the most sensitive, followed by H-2k and H-2d. Experiments using passive transfer of serum as well as the complement inhibitors suramin and flufenamic acid indicated that variations in complement levels under control of H-2 may be responsible for the effects described. Cyproheptadine, a blocker of serotonin and histamine receptors, and imidazol-alpha-ketoglutarate, an inhibitor of thromboxane synthesis, inhibited PSA, indicating that platelet aggregation, possibly mediated by activated components of the complement cascade, is an important feature in the development of PSA reactions in this system. Differences between strains for protection by cyproheptadine and for the effect of complement inhibitors indicated a role of early components of the classical pathway in this model.