The long-term objective of this proposal is the elucidation of immunological and other mechanisms leading to helminth rejection of killing in the gut. Intestinal helminths cause significant disease in man and domestic animals and are informative probes of intestinal immune function. In T. spiralis infected rats, we have demonstrated that the intestine is the site of development and expression of three distinct immune responses-rapid expulsion (RE), adult worm rejection and anti- newborn larvae activity. Furthermore we have also shown that a unique population (or subpopulations) of thoracic duct lymphocytes present at day 3/4 post infection can adoptively transfer both adult worm rejection, and, in conjunction with antibody, RE (RE initiators). In a separate system, we have demonstrated passive transfer of intestinal anti-newborn larvae immunity with immune serum. The fact that protective cells are present at day 3/4 and migrate preferentially to the gut in large numbers is persuasive evidence that these cells are the natural mediators of rejection. Thus, for the first time a detailed analysis of the phenotype, migration pattern and ultimate effects of the natural cellular effectors of helminth rejection can be performed. Analysis of cell migration will be done by radiolabelling 0X-8-OX-22-and RE(in) cells using 125 lododeoxyuridine. We will determine whether each protective function is a property of the same cell subset by phenotypic analysis using a panel of mAbs cell affinity chromatography and panning for functional testing of isolated T cell subsets. Function will be assessed by a combination of allogeneic cell transfers, bone marrow transplants to irradiated T cell recipients and in vitro studies. Changes will be monitored by histopathological and histochemical analysis of the gut and by worm burden. Serum effectors of RE and NBL larvae immunity will be defined by fractionation of serum into lgG (and its subclasses) IgM and IgE fractions. In addition, experiments with RE-functional (in neonates) monoclonal IgG1 and IgG2c antibody are planned. Purified functional immunoglobulin will be radiolabelled (1251) and examined for its adherence to cells in the gut prior to challenge (to help define reactive cells) and to infectious muscle larvae collected from the gut lumen 20-30' after challenge. These procedures are expected to provide new insight into functional mechanisms of protection in the gut against the nematode T. spiralis.