Live intracellular <i>M. kansasii</i> activates caspase-1 and induces IL-1β secretion in THP-1 derived macrophages.

<p>Macrophages were infected by <i>M. kansasii</i>, followed by analysis of caspase-1 activation and IL-1βsecretion in culture media. (<b>A</b>) The amount of IL-1β secreted from infected macrophages at an MOI of 0.1–10 for 16 h. <b>(B</b>) The secreted mature caspase-1 and IL-1β from infected macrophages at an MOI of 0.1–25 for 16 h. (<b>C</b>) Macrophages were challenged with live or heat-killed <i>M. kansasii</i> at an MOI of 10 for 16 h. Secreted IL-1β was measured by ELISA (left panel). Caspase-1 p20 and 17-kDa IL-1β were analyzed by immunoblotting (right panel). (<b>D</b>) Macrophages were treated with 1 µg/ml CytoD for 60 min to block phagocytosis and then incubated with <i>M. kansasii</i> at an MOI of 10 in the presence or absence of CytoD. Secreted IL-1β was measured by ELISA (left panel); activated caspase-1 and mature IL-1β were detected by Western blot analysis (right panel). Cells treated with 1 µg/ml LPS for 3 h and 1 µM nigericin for 1.5 h were used as control (LPS+Nig). Values represent the mean ± standard deviations of at least three independent experiments.