GM-CSF IS REQUIRED FOR THE PSEUDOMONAS EXOTOXIN A-INDUCED PROLIFERATION OF IMMATURE T-CELLS IN ATHYMIC MICE

Previous studies have demonstrated that Pseudomonas exotoxin A stimula ted the proliferation of immature T lymphocytes within the splenocytes of athymic mice. These studies were performed to determine which lymp hokines were involved in the proliferation of the immature T cells. Th e results of this study indicate that exotoxin A does not induce the p roduction of interleukin-a or tumor necrosis factor from B cell-deplet ed splenotypes from athymic mice. However, exotoxin A does induce the production of granulocyte-macrophage colony-stimulating factor (GM-CSF ) from B cell-depleted splenocytes. Furthermore, the GM-CSF was shown to be produced by a Thy1(+), CD4(-), CD8(-) T lymphocyte. The addition of anti-GM-CSF antibody abrogates the exotoxin A-induced proliferatio n of B cell-depleted splenocytes from athymic mice. Thus, these data i ndicate that exotoxin A induces the production of GM-CSF from immature T lymphocytes within the splenocytes of athymic mice and the exotoxin A-induced proliferation of these immature T cells is dependent on the presence of GM-CSF. (C) 1995 Academic Press, Inc.