TYPE-I HYPERSENSITIVITY REACTIONS IN INTESTINAL MUCOSAE FROM RATS INFECTED WITH FASCIOLA-HEPATICA

Type I hypersensitivity reactions in the intestinal tract of sensitize d animals may contribute to resistance to reinfection with Fasciola he patica. Colonic mucosae isolated from previously infected rats were vo ltage clamped in Ussing chambers. Antigen was prepared as a crude homo genate from adult liver fluke. Assay of serum antibodies against fluke antigen confirmed sensitization. Antigen challenge evoked a rapid ons et, transient inward current in sensitized but not in control preparat ions. Chloride secretion accounted for at least part of the response s ince the loop diuretic bumetanide reduced the effect of antigen by 61% . Anti-rat IgE mimicked the response to antigen and desensitized tissu es to subsequent antigen challenge. Local synthesis of eicosanoids may mediate the response to antigen since the cyclo-oxygenase inhibitor p iroxicam reduced the response by 76%. In contrast, mepyramine which is a histamine receptor antagonist did not alter the ion transport respo nse evoked by antigen. Tetrodotoxin reduced the response to antigen by 53% implicating intrinsic neurons within the lamina propria as effect or cells in the responses of this tissue to antigen. We propose that a ntigen stimulation of electrogenic chloride movement and consequent fl uid secretion in vivo may contribute to a local effector mechanism in prevention of reinfection of previously sensitized hosts.