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The relationship of Tritchomonasfoetus adhesion to mammalian cells and cytotoxicity to these targets was investigated. High-adherence and low-adherence lines of T. foetus, derived by repeated adhesion to HeLa cells, showed high and low cytotoxicity, respectively, to HeLa cells. When parasites were separated from targets by membranes (0.4-tm pore size), no cytotoxicity was detectable. Monoclonal antibodies elicited against T. foetus that lowered adhesion also lowered parasite-mediated cytotoxicity. Flow cytometry experiments revealed that the levels of an adhesionand cytotoxicity-blocking antibody bound to the surface of high-adherence clones of T. foetus were higher than those in low-adherence clones. Western blots of parasite extracts separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were probed with an anti-T. foetus antibody. A molecule with a molecular weight of -190,000 composed of subunits with molecular weights of 140,000 to 150,000 and =65,000 was identified. Immunoprecipitation experiments with metabolically labeled T.foetus and the same antibody confirmed that similar subunits were synthesized by the parasite. These results indicate that adhesion of T. foetus to mammalian cells is an important step in cytotoxic damage of these targets and that a surface adhesin on the parasite is involved in the adhesion mechanism.

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