NOS2 and infection: We measured the induction of two antimycobacterial genes, that for the inducible nitric oxide synthase (iNOS) (nos2) [45] and that for the immunity-related GTPase family M member 1 gene (irgm1) [46] and found that while there was a similar expression of nos2 in both groups of Mtb-infected mice, there was reduced expression of irgm1 by AID−/−μS−/− mice at early stages of infection (Figure 3E), consistent with a reduced expression of IFN-γ at this same time points (Figure 3B).