FIG. 6.

Failure of B. pseudomallei-infected macrophages to activate IRF-1 and iNOS expression in response to postinfection IFN-γ stimulation. Mouse macrophages were infected with B. pseudomallei at an MOI of 2:1 as described in Materials and Methods. In the postinfection stimulation (post) experiment, IFN-γ (10 U/ml) was added 4 h after the cells were infected with B. pseudomallei. The infected cell cultures were incubated for one more hour before excess IFN-γ was removed. The cell cultures were then incubated for a further 3 h, the macrophages were lysed, and the levels IRF-1 and iNOS in the lysates were determined by immunoblotting. For the costimulation (co) experiment, the macrophages were infected with B. pseudomallei in the presence of IFN-γ (10 U/ml). After 1 h of incubation, the macrophages were washed three times with PBS and cultured for three more hours before the levels of IRF-1 and iNOS in the cell lysate were determined by immunoblotting.