Previously in our murine TB model using the H37Rv strain was observed a biphasic increase in the gene expression of Fox-p3, IDO, and HO-1 (Hernández-Pando et al., 2008), with high expression of these molecules after one week, followed by a decrease and an increase again after one month of infection (Hernández-Pando et al., 2008), which is the time point when in our model start pneumonia formation and there is high production of IFN-γ (Hernandez-Pando et al., 1996). This evidence concerns the gene IFNG and susceptibility to pneumonia measurement.