ER Stress-Mediated Apoptosis in Mtb Infections Figure 1. Mtb H37Rv infection induces apoptosis and caspase activation. (A) Raw264.7 cells were screened for induction of apoptosis using Annexin-V/PI staining after 48 h infection with Mtb H37Rv at a MOI of 1. Staurosporine (500 nM) was used for making positive control for apoptosis. After washing and Annexin V-/PI staining, cells were analyzed by flow cytometry. Data are respresentative of at least three independent experiments with similar results. (B) Quantitative analysis of the percentage of Annexin V-positive cells as described in B. ***, P,0.001 (C) Cellular levels of caspase- 3, caspase-9, and caspase-12 during Mtb-infection in Raw264.7 cells. (D) The effect of caspase inhibitor z-VAD-fmk on the CHOP expression in Mtb- PLoS ONE | www.plosone.org 3 December 2011 | Volume 6 | Issue 12 | e28531