Chronic inflammation coincided with compromised Th1 and CD8+ CTL responses whereas Th2/Treg cytokines ie. IL-13, TGF-β and IL-10, and several inhibitory checkpoint molecules such as IDO, LAG-3 and TIM-3 were enhanced in Mtb-infected tissues, supportive of an immunosuppressive environment in the TB lesions (133). This evidence concerns the gene IDO1 and tuberculosis.