Studies on the inhibition of rapid expulsion of Trichinella spiralis in rats.

A variety of inhibitors was examined for their ability to interfere with the expression of rapid expulsion (RE) of challenge Trichinella spiralis infections in rats. Inhibitors of immediate hypersensitivity, prostaglandin release, peristalsis, or complement function, did not impair RE when administered to immune rats. Induction of intestinal anaphylaxis against T. spiralis or ovalbumin by passive serum transfer to intestinally primed rats (prior infection with Heligmosomoides polygyrus) or administration of the histamine liberator 48/80 also failed to stimulate RE. In contrast, irradiation or cortisone treatment 1, 3 or 5 days before challenge inhibited RE. We conclude that immediate hypersensitivity is not the terminal mediator of RE and plays a minor role or none at all. The effects of cortisone and irradiation suggest a major involvement by lymphoid cells in the RE reaction.