SR-A/MARCO-mediated ligand recognition promotes NALP3-mediated IL1β secretion. WT, SR-A^−/−, MARCO^−/−, and DKO Mϕ (all n = 4) were stimulated with 100 μg/mL of polyI, polyC (A), or 20 MOI of inactivated NM (B) for 6 hours and then pulsed for 5 minutes with 1mM ATP. After a further 6 hours, supernatants were harvested and the levels of IL1β were measured by ELISA. (C) WT, SR-A^−/−, MARCO^−/−, and DKO mice were challenged intraperitoneally with 10⁵ CFU of inactivated NM, followed by a short ATP pulse 2 hours later. Levels of IL1β in peritoneal lavage fluid were measured by ELISA and compared among strains. (D) -Fold changes in IL1β mRNA expression are shown after stimulating Bg-PM from WT, SR-A^−/− and MARCO^−/−, and DKO mice with 20 MOI of NM for 4 hours. Each treatment condition was analyzed in triplicate and data are representative of 3 independent experiments. (E) Bg-PM from WT, SR-A, and MARCO, DKO mice were primed with 20 MOI of inactivated NM, washed to remove excess bacteria, and then further stimulated overnight with either 250μg/mL of silica or asbestos. IL1β levels were measured by ELISA. NM, silica, and asbestos alone did not induce any secreted IL1β (data not shown). Each treatment condition was measured in triplicate and data presented are representative of 3 independent experiments. Statistical significance for panels A, B, and E was assessed by 2-way ANOVA with Bonferroni posttest. One-way ANOVA with Dunnett multiple comparison test was used to assess statistical significance for panel C. *P ≤ .05; ***P < .001.