FIG. 2.

Induction of NO by commercially available S. aureus, B. subtilis, and S. sanguis LTA in the presence of polymyxin B. RAW 264.7 macrophages were stimulated with increasing concentrations of S. aureus (A), B. subtilis (B), and S. sanguis (C) LTA in either the absence (solid columns) or the presence (hatched columns) of 10 μg of polymyxin B (PMB)/ml for 20 h before supernatants were taken for a nitrite assay as described in Materials and Methods. Cell viability was not affected by treatment with LTA either alone or in combination with polymyxin B, as judged by more than 95% cellular exclusion of trypan blue in parallel cultures. Data represent averages of triplicate samples ± standard errors of the means. Experiments were repeated three times under equivalent conditions.