Anthrax lethal toxin-induced mitogenic response of human T-cells.

Bacillus anthracis lethal toxin (PALF) stimulated the proliferation of human peripheral blood T-cells in vitro. Activation of T-lymphocytes by PALF required the presence of monocytes and did not result from a collaborative effect between T-cells and B-cells. PALF acted directly on monocytes and independently of T-cells. The monocytes contributed to the proliferation of T-cells by secretion of mediator(s). The mitogenic activity of the lethal toxin was dependent on its metalloprotease activity.