Inhibition of passive systemic anaphylaxis in guinea pigs by Trichinella spiralis infection.

Thirty of 33 guinea pigs experimentally infected with Trichinella spiralis survived passive systemic anaphylactic reactions which were fatal for 32 of 33 uninfected controls. Guinea pigs were infected with viable excysted trichinella larvae 20 to 32 days before they and uninfected controls were sensitized by intracardiac injection of rabbit anti-bovine serum albumin. Animals were challenged 24 hours later by intracardiac injection of bovine serum albumin. Respiratory anaphylaxis was observed in all challenged animals. Protection from passive anaphylaxis in parasitized guinea pigs was most likely due to preemption of mast cell receptors by parasite-induced antibody with consequent blockage of passive sensitization.