FIGURE 2.

GAS-induced macrophage apoptosis is caspase-dependent. A, activity of apoptotic caspases (DEVDase) was measured with the fluorescent substrate Ac-DEVD-AFC in lysates of cells infected with GAS but not L. lactis control. B, induction of macrophage apoptosis is inhibited by the general caspase inhibitor Q-VD-OPH. C, high extracellular KCl (130 mm) inhibits GAS-induced macrophage apoptosis. ActD, actinomycin D. D, caspase-1-specific inhibitor YVAD-CHO decreases GAS-induced macrophage apoptosis. E, caspase-1^–/– mouse macrophages are more resistant to GAS-induced apoptosis. t = 4 h for all experiments. * = p < 0.05 and ** = p < 0.005. All experiments were performed in triplicate and repeated three times. MOI, multiplicity of infection.