To identify weather M. tuberculosis-induced necrosis of macrophages is related to the intrinsic apoptotic pathway, host cells were treated with irreversible caspase-9 inhibitor Z-LEHD-FMK.TFA (Sigma) and levels of cytotoxicity were determined by 3, 5, 7 and 9 days post-infection. Here, CASP9 is linked to infection.