FIGURE 8.

SLO induction of macrophage apoptosis blunts immune activation. A, role for SLO in apoptosis induction observed upon GAS infection of primary BMD macrophages. B, reduced TNFα levels in supernatants of primary mouse macrophages infected with SLO-expressing strains. C, accelerated apoptosis induced by WT GAS reduces levels of inflammatory cytokine IL-1β from macrophages compared with infection with the ΔSLO mutant. D, TNFα and IL-1β gene transcripts are significantly up-regulated by infection with both WT GAS and the ΔSLO mutant. Experiments performed in triplicate and repeated three times. E, decreased TNFα detected in the blood of mice 6 h after intravenous infection with WT GAS versus the ΔSLO mutant. IV, intravenous.