FIG 4.

C. burnetii infection does not elicit elevated caspase-1 activity or promote cell lysis indicative of pyroptosis. hAMs were left uninfected (UI), treated with LPS and ATP (+), or infected with avirulent C. burnetii for the indicated times. (A) Active caspase-1 was detected with a fluorescent FAM-FLICA probe. Avirulent C. burnetii does not trigger significant caspase-1 activity. (B) LDH present in the supernatant was measured as an indicator of cell lysis. Values for experimental samples were calculated as percentages of the positive-control value (set to 100%). Data are representative of at least three separate experiments using cells from at least two separate donors, and error bars represent the standard deviation from the mean. n.s., not significantly different from value for uninfected cells. C. burnetii-infected cells do not release significantly more LDH than uninfected hAMs.