FIG. 7.

l-Arginine-dependent killing of B. anthracis in spore-infected macrophages. (A) Primary murine peritoneal macrophages (1 × 10⁶ cells/ml) were infected with spores (1 × 10⁵ spores/ml) prepared from sonicated B. anthracis strain Sterne 34F2 and treated with (▪) or without (□) L-NIL (1 mM). The infected macrophages were incubated for 1, 3, 5, and 24 h in 5% CO₂ at 37°C, washed, and lysed for viable count plating, and numbers of CFU were determined. The data are expressed as log values. Log kill values were as defined in Materials and Methods. (B) Macrophages (1 × 10⁶ cells/ml) were infected with spores (1 × 10⁵ spores/ml) prepared from sonicated B. anthracis strain Sterne 34F2 in culture medium with (□) or without (▪) l-arginine. The infected macrophages were incubated for 1, 3, 5, and 24 h in 5% CO₂ at 37°C, washed, and lysed for viable count plating, and numbers of CFU were determined. The data are expressed as differences in log values. Data are shown as means ± standard deviations of values obtained from two independent experiments, each conducted in duplicate.