Induction of suppressor macrophages in mice by Fusarenon-X.

Intraperitoneal injection of Fusarenon-X into BALB/c mice, a mycotoxin produced by Fusarium nivale Fn 2B, depressed polyclonal antibody formation of splenic lymphocytes in response to pokeweed mitogen (PWM). This inhibitory activity was found to reside in the surface immunoglobulin-negative spleen cell fraction of Fusarenon-X-treated mice, sIg-(FX), which comprised mainly T lymphocytes and smaller number of non-lymphocytic cellular elements. However, reconstitution experiments for in vitro antibody formation provided evidence that T lymphocytes from Fusarenon-X-treated mice, T(FX), which were separated from non-lymphocytic cells by use of carbonyl iron/magnet, were as effective as T lymphocytes from normal mice, T(N), in supporting antibody formation. Furthermore, addition of non-lymphocytic cells, NL(FX), or adherent cells, AD(FX), prepared from spleen cells of Fusarenon-X-treated mice to normal spleen cells strongly inhibited in vitro antibody formation against PWM or a bacterial lipopolysaccharide (LPS). These results strongly indicated that Fusarenon-X induced non-lymphocytic suppressor cells in the spleen of the treated mice which had features in common with activated macrophages.