ROLE OF T-LYMPHOCYTES IN SECRETORY RESPONSE TO AN ENTERIC NEMATODE PARASITE - STUDIES IN ATHYMIC RATS

Athymic (nude) rats have been used to assess the role of thymus-depend ent T cells in the control of the intestinal response following infect ion with the enteric parasite, Nippostrongylus brasiliensis. Tissues f rom infected rats were excised on days 4, 7, 10, and 21 postinfection (p-i) for physiological and morphological studies; uninfected (day 0) rats served as controls. In response to the worm burden, jejunal tissu es displayed a secretory response, indicated by an elevated baseline s hort-circuit current (I-sc) on days 7 and 10 p-i, and were more respon sive to histamine than control tissues. Despite this enhanced secretor y response, similar to 35% of the worm burden was still present on day 21 p-i (compared with expulsion of >95% by day 14 p-i in normal rats) . Mast cell activation and hyperplasia, increased goblet cell (implyin g increased mucus synthesis) and intraepithelial leukocyte numbers, an d abnormalities in I-sc responses after electrical stimulation of ente ric nerves were identified following infection. These events in nude r ats were attenuated or delayed in onset as compared with conventional immunocompetent rats. Our results support the postulate that thymus-de pendent T cells regulate the timing and/or nature of the mucosal respo nse to enteric parasitic infections. However, ion secretion was not al tered in the absence of T cells and, therefore, is more likely to be a consequence of mast cell activation.