NOS2 and infection: Between weeks 3 and 7 of infection, in the lungs of B-IL-6KO and WT mice we observed a marked (~8-fold) and equal increase in expression of the inos gene (Figure 5С) encoding inducible NO synthase (iNOS), the enzyme playing a pivotal role in the mycobacterial killing in mice (45) and a key marker of the M1 macrophage subset.