CYTOTOXIC EFFECTS OF ANTHRAX LETHAL TOXIN ON MACROPHAGE-LIKE CELL-LINE J774A.1

The cytotoxic effects of anthrax lethal toxin purified from an avirule nt strain were examined on mouse macrophage-like J774A.1 cells. Cell d eath induced by high concentration of purified lethal toxin had the ch aracteristics of necrosis. At lower concentrations, the toxin caused n o morphological change and most of the cells were viable. Interestingl y, apoptotic cells were observed when the cells were preincubated with a serine/threonine phosphatase inhibitor, calyculin A, and then expos ed to a toxin concentration of 0.1 mu g/ml. This is the first report t hat lethal toxin of the anthrax bacillus can induce both necrosis and apoptosis and that protein phosphatases are implicated in the regulati on of bacterial toxin-induced apoptosis.