The relative contribution of polarized macrophages to the maintenance of tolerance is unknown. We examined their roles by in vivo adoptive transfer immunotherapy of M0, M1 and M2a macrophages as pre-treatment of colitis. In other experiments, M2a macrophages were used as pre-treatment or treatment of established colitis followed by immunotherapy with nTreg cells. Survival, weight gain, tissue infiltration, iTreg and Th17 cell development, T cell activation, and the frequency of proinflammatory cytokines were used as outcome measurements. Pre-treatment with M2a but not M1 macrophages increased the development of iTreg and Th17 cells. M2a macrophages used as pre-treatment or in treatment of established colitis allowed for successful therapy with nTreg cells.