Unique phenotype of resolution-phase macrophages is preserved in response to inflammatory stimuli ex vivo. Macrophages were isolated from a 72-hour peritonitis that either resolved (0.1 mg zymosan or rM macrophages, □) or progressed to systemic inflammation (10 mg zymosan or M1 macrophages, ■) and incubated for 6 hours ex vivo to determine profiles and levels of (A) cytokines and chemokines indicative of established M1 and M2 macrophage phenotype. Having established that rM macrophages secrete predominantly anti-inflammatory IL-10 and comparatively fewer proinflammatory mediators, expression of other inflammatory markers was determined including (B) iNOS as well as (C) COX 2 and COX 2–derived PGD₂ and intracellular markers of M2 phenotype including (D) mannose receptor as well as (E) cAMP. (F,G) Finally, we determined that exposure of these resolution-phase macrophages to a range of inflammatory stimuli did not alter their phenotype, which remained robust upon exposure to TLR ligands. n = 6-8 mice per group. *P ≤ .05, as determined by ANOVA, followed by Bonferroni t test or 2-tailed Student t test, with data expressed as mean plus or minus SEM.