Figure 3

Dendritic cell death after M. tuberculosis H37Ra infection is caspase-independent and proceeds without the activation of caspase 3 and 7. A. DCs were infected with live Mtb H37Ra at MOI 10, in the presence or absence of the pan-caspase inhibitor, Q-VD-OPh (20 μM). Cell death was measured by propidium iodide exclusion 72 h post-infection. ** p < 0.01 vs. uninfected. Data represents means (± SEM) of 3 separate donors. B. As a positive control, DCs were treated with cycloheximide (5 μg/ml) or staurosporine (1 μM) in the presence or absence of Q-VD-OPh for 72 h. Nuclei were stained with Hoechst and visualised by fluorescence microscopy. C. DCs were infected with live/dead Mtb H37Ra or γ-irradiated H37Rv at MOI 10. Caspase 3/7 activity was assessed at 24 h, 48 h and 72 h in triplicate wells. Cell death was measured in parallel by propidium iodide exclusion(upper panels). (U = uninfected, LH37Ra = live H37Ra, sH37Ra = streptomycin-killed H37Ra, iH37Rv = γ-irradiated H37Rv, STS = staurosporine, CHX = cycloheximide.) * p < 0.05 vs. uninfected. ** p < 0.01 vs. uninfected. *** p < 0.001 vs. uninfected. Data represent means (± SEM) of 1 donor representative of 5.