HOIL-1L is required for MDP-induced peritonitis in vivo. WT and HOIL-1L^−/− mice were injected i.p. with PBS or MDP to induce peritonitis. 5 h later, IP wash fluid was analyzed for IL-1β (a) and IL-6 (b) levels by ELISA and infiltrating Ly6G/CD11b double-positive neutrophils (c and d) were quantified by flow cytometry (biological n = 8 from three independent experiments). All data are presented as the mean ± SEM. *, P < 0.00015 by a Student’s t test.