Figure 1: Mycobacterium tuberculosis LpqH lipoprotein induces caspase-dependent macrophage apoptosis. (a) Peripheral blood monocyte-derived human macrophages were incubated for 1 h with LpqH. As a control, cells were incubated with 100 μg protein present in 19-kDa nitrocellulose strips of native M. smegmatis (M. smeg-N), which as seen by immunoblot do not contain LpqH (not shown). Apoptosis was measured with a nucleosome ELISA kit. Apoptosis is expressed as the mean ± SE arbitrary units (a.u.)of four independent experiments. Statistically significant differences are indicated; . (b) To determine the role of caspases, whole-cell protein extracts of MO made apoptotic by incubation with 5 μg LpqH were separated by SDS-PAGE and immunoblot analysis was performed with antibodies to caspases 8, 3, and 9. Procaspases and cleaved caspases are shown.