Male C57/Bl6, IL-10−/− and inos−/− mice were obtained from The Jackson Laboratory, and mkk3−/− and hmox−/− mice were generated by R. Flavell (Yale University School of Medicine, New Haven, CT) and S. Yet (Harvard Medical School, Boston, MA), respectively. All wild-type and genetically deficient mice used in this study were on the C57/Bl6 background and matched for age and sex in all experiments. IL-10−/− mice were fed a chow mixed with 200 ppm piroxicam (Sigma-Aldrich) for 5 d as indicated in Results. Pelleted diets were prepared by Dyets, Inc. All animals were housed in accordance with guidelines from the American Association for Laboratory Animal Care and Research Protocols and were approved by the Institutional Animal Care and Use Committee of the University of Pittsburgh. At the end of the study period, animals were killed using excess CO2 inhalation. Immediately afterward, blood by cardiac puncture (carboxyhemoglobin determination), spleens, intestinal tissue samples, and femurs were collected. BM-derived macrophages and splenocytes were cultured as described previously (26 (link)).