Effects of staphylococcal enterotoxins on human neutrophil functions and apoptosis

Staphylococcal enterotoxins have marked effects on the properties of T cell s and monocytes and have recently been reported to affect neutrophil functi on, In this study, we investigated the abilities of staphylococcal enteroto xins A and B and toxic shock syndrome toxin 1 to affect respiratory burst a ctivity and to delay apoptosis in human neutrophils. When cultures containi ng approximately 97% neutrophils were tested, the toxins all delayed neutro phil apoptosis in a dose-dependent manner and induced the expression of Fc gamma RI on the neutrophil cell surface, These effects on apoptosis and exp ression of Fc gamma RI were largely abrogated by the addition of a neutrali zing anti-gamma interferon antibody. Similarly, the effects of these toxins on phorbol ester-induced chemiluminescence were decreased after neutraliza tion of gamma interferon, These effects on neutrophil function were mimicke d by the addition of conditioned medium from peripheral blood mononuclear c ells incubated with the toxins, and again, neutralizing anti-gamma interfer on antibodies largely negated the effects, However, when highly purified ne utrophils prepared by immunodepletion of T cells and major histocompatibili ty complex class II-expressing cells were analyzed, the toxins were without effect on apoptosis and Fc gamma RI expression, but granulocyte-macrophage colony stimulating factor and gamma interferon could still delay apoptosis , These data indicate that these toxins have no direct effect on neutrophil apoptosis but can act indirectly via the production of T-cell-derived and monocyte-derived cytokines, It is noteworthy that such effects are detected in neutrophil suspensions containing only 3% contamination with T cells an d other mononuclear cells.