FIG. 6.

Type III secretion pathway, IpaB, and IpaC are necessary for S. flexneri-induced neutrophil cytotoxicity. Several mutants were used under nonopsonic conditions at an MOI of 100:1 to infect neutrophils. M90T (wild type), SF401 (mxiD1), SF620 (ipaB2), SF621 (ipaC2), BS176 (virulence plasmid cured). (A) The release of lactoferrin was measured 1 h after infection. (B) The cytotoxic effect of Shigella was measured 2.5 h after infection, using LDH and β-glucuronidase as markers of cytolysis. The results are expressed as the means ± standard deviations of three to five experiments. nd, not determined.