SR-A and MARCO bind MDP and enhance NOD2 response. (A) SR-A (left panel) and MARCO (right panel) bind to various polyanionic ligands. A known ligand (dextran sulfate, Dx-SO4) and a non-ligand (chondroitin sulfate, Ch-SO4) for SR-A and MARCO were used to coat wells of a 96-well plate, along with MDP. SR-A–specific ligand activity was determined by overlaying postnuclear cell lysates from WT and SR-A^−/− BMMϕ and detected with specific anti–SR-A monoclonal antibody 2F8. Similarly, recombinant sMARCO and specific anti–MARCO monoclonal antibody ED31 were utilized to identify MARCO specific binding. (B) After MDP stimulation, SR-A^−/−, MARCO^−/−, and DKO Mϕ produced decreased levels of TNF-α (left panel) and IL6 (right panel) compared with WT cells. IFN-γ–primed Bg-PM from each mouse strain were stimulated with 100 μg/mL of MDP for 16 hours. Levels of TNF-α and IL6 were measured by ELISA. (C) Decreased levels of TNF-α (left panel) and IL6 (right panel) were produced in the peritoneal cavity of SR-A^−/−, MARCO, and DKO mice injected intraperitoneally with 100 μg of MDP or an equal volume of PBS. After 2 hours, animals were killed and peritoneal lavage performed using 1 mL of PBS. Levels of TNF-α and IL6 were measured by ELISA. Statistical significance for panels A and B was assessed by 2-way ANOVA with the Bonferroni posttest. One-way ANOVA with Dunnett multiple comparison test was used to assess statistical significance for panel C. ***P < .001