PDCD1 and tuberculosis: Researchers have found that PD-1-deficient mice develop large necrotic lesions and a higher mycobacterial burden in their lungs.[26] Although it is unclear what role the PD-1/PD-L1 signal pathway plays in TB infection, murine studies have shown that T cells lacking PD-1 mediated inhibition may promote rather than control the infection of TB.[27,28] Based on the aforementioned reports, the association between immunotherapy and TB infection remains unclear.