Immediate hypersensitivity reactions in epithelia from rats infected with Nippostrongylus brasiliensis

Colonic epithelia from rats infected with the nematode Nippostrongylus brasiliensis have been studied under short circuit conditions and in response to challenge with worm antigen. Challenge from the serosal but not the mucosal side with antigen caused a transient increase in inwardly directed short circuit current. No effects were observed in comparable tissues from noninfected animals. Simultaneous measurements of short circuit current and of the fluxes of sodium or chloride ions showed there was an increase in electrogenic chloride secretion and an inhibition of electroneutral sodium chloride absorption, associated with antigen challenge. This result, together with the inhibitory effects of piretanide on the response to antigen challenge, indicate that chloride ions are a major carrier of the short circuit current response. However, the equivalence of the biophysical response to ion fluxes was not established, there being an excess of chloride secretion. The mast cell stabilizing agent, FPL 52694, significantly inhibited the current responses to antigen, while cromoglycate and doxantrazole were ineffective. Mepyramine, an H1-receptor antagonist, and indomethacin, an inhibitor of fatty acid cyclo-oxygenase, were without effect on the responses to antigen challenge. Anti-rat IgE produced qualitatively similar responses to antigen in both normal and sensitized colonic epithelia. However, the responses were significantly greater in tissues derived from infected animals. Maximally effective antigen concentrations prevented subsequent responses to anti-rat IgE in sensitized tissues, while anti-rat IgE only attenuated the responses to antigen. The ways in which antigen challenge modifies epithelial function is discussed, particularly in relation to its possible role in promoting rejection of the nematodes during secondary infection.