Immunotoxic effects of T-2 toxin on cell-mediated immunity to listeriosis in mice: comparison with cyclophosphamide.

Immunotoxic effects of T-2 toxin and cyclophosphamide on cell-mediated resistance were evaluated in mice exposed to Listeria monocytogenes infection. Mice were inoculated intraperitoneally with 4.0 X 10(5) (LD50) or 4.0 X 10(4) (nonlethal) L monocytogenes and were treated with 4.0 mg of T-2 toxin/kg of body weight or 180 mg of cyclophosphamide/kg. The immunosuppressive effect of the toxin and cyclophosphamide was indicated by the rapid growth of Listeria and significant (P less than 0.005) increases in mortality because of listeriosis. Necrosis and depletion of lymphoid tissue, lymphopenia, and significant (P less than 0.005) decreases in the influx and number of lymphocytes and macrophages occurred in Listeria-elicited peritoneal exudates and at sites of infection in the liver and spleen of the toxin- and cyclophosphamide-treated mice. Immunotoxic effects of T-2 toxin and cyclophosphamide were comparable and attributed primarily to the depletion of T lymphocytes and the subsequent failure of surviving immunologically committed T cells and T-cell dependent immune-activated macrophages to clear the host of bacteria.