Figure 4.

Involvement of LOS in licensing inflammasome activation in innate immune cells. Isolated human neutrophils were stimulated by the parental wild-type N. meningitidis FAM20 or its LOS-deficient mutant strain IpxA (MOI of 10), by purified LOS alone (1 μg/mL), lpxA + LOS, or FAM20 + TLR4 signalling blockers (anti-hCD14-IgA 500 ng/mL, LPS-RS ultrapure 1 μg/mL, and polymyxin B 10 μg/mL) for 2 h and 6 h, respectively (a and b). Isolated neutrophils were primed by preincubation for 1 h with Pam3CSK4 (2 μg/mL) before bacterial stimulation (c and d). Caspase-1 activity of isolated neutrophils (a and c) was determined by flow cytometry and is presented as fold increase in median fluorescence intensity (MFI) normalized to unstimulated cells. IL-1β release (b and d) was measured from culture supernatant by ELISA. Bars represent mean ± SEM; n = 3.