Inflammatory environment dictates macrophage phenotype. rM cells from a 72-hour zymosan (0.1 mg)–induced peritonitis were labeled with PKH26-PCL^red and adoptively transferred at 72 hours to mice bearing a 10 mg zymosan (nonresolving inflammation) peritonitis and found not to trigger resolution as defined by little alterations in (A) total as well as individual cell numbers (PMNs, MΦs, and innate-type lymphocytes, not shown) determined 24 hours later. However, adoptively transferred rMs (identified by being PKH26-PCL^red) were isolated from the nonresolving milieu after 24 hours using FACSAria and were found to synthesize more (B) TNFα than native rM cells with little change in (C) IL-10, indicating that despite the robustness of ex vivo stimulation reported in Figure 2F,G, the inflammatory environment of whole animal systems dictates cellular phenotypes. n = 6 mice per group. * indicates P ≤ .05, and **P ≤ .01, as determined by ANOVA, followed by Bonferroni t test with data expressed as mean plus or minus SEM.