IDO1 and infection: Thus, the experimental decrease of Treg cells and IDO in BALB/c mice infected with mild virulence reference strain H37Rv is beneficial, which is in agreement with the previous observations that show delayed recruitment of effector cells by Treg cells in the lung during early TB (Shafiani et al., 2010), when Tregs were depleted in the early phase of infection, effector T cells migrated correctly and limit the expansion of bacilli load in progressive phase but is not enough to change the course of infection.