FIG. 6.

Nitrite production in B. anthracis spore-infected macrophages. Primary murine peritoneal macrophages (1 × 10⁶cells/ml) were pretreated with (black bars) or without (white bars) IFN-γ (100 U/ml) overnight and infected with B. anthracis spores (1 × 10⁶ spores/ml) prepared from nonsonicated B. anthracis Sterne 34F2 (A) and sonicated B. anthracis Sterne 34F2 (B). Cell culture supernatants were collected, and nitrite production was determined at 1, 3, 5, and 24 h postinfection utilizing the Griess reaction assay. *, significance at P < 0.01 compared to 1 h postinfection. Differences in nitrite production between results shown in panels A and B are in agreement with data presented in Fig. 4.