FIGURE 1.

Live intracellular GAS induce rapid dose-dependent macrophage apoptosis. A, dose-dependent induction of macrophage apoptosis by GAS (t = 4 h). B, GAS induction of apoptosis proceeds more rapidly than control induction by actinomycin D, multiplicity of infection (MOI) = 10 bacteria/cell. C, GAS must be viable to induce macrophage apoptosis. D, internalization (phagocytosis) of GAS by the macrophage is required for apoptosis induction. * = p < 0.05, ** = p < 0.005, and *** = p < 0.0005. All experiments were performed in triplicate and repeated three times.