TLR4 and lung carcinoma: In tuberculosis, which is associated with a higher lung cancer risk (50), Mycobacterium bovis Bacille–Calmette–Guerín (BCG) infection induces TLR2 and TLR4 expression in mouse MDSCs, further upregulating CD40, PD-L1, and CD69 expression in both G-MDSCs and M-MDSCs as well as iNOS expression, leading to increased nitric oxide (NO) production required for the suppression of T cell proliferation in BCG-infected mice (51).