CD4+ T-cells are important in regulating macrophage polarization in C57BL/6 wild-type mice

During activation, macrophages undergo physiological changes affecting their surface protein expression and cytokine production and have been subsequently categorized into M1 (classically-activated) and M2 (alternatively-activated) macrophages. It remains unclear which lymphocyte population provides the immune microenvironment to regulate macrophage polarization. In this study, we establish a functional and phenotypic profile of peritoneal macrophages from C57BL/6 wild-type mice. We also showed that Rag1−/− and Rag2−/−γc−/− mice have similar, exaggerated M1 characteristics in comparison to control mice, suggesting that NK and/or NK-T cells may not be essential in this process. By controlling for environmental factors, we determine that lymphocyte-derived cytokines, rather than inherent properties of macrophages themselves, are crucial for their regulation. Lastly, we report that macrophages from CD4−/− mice display an M1 profile, suggesting that CD4+ T-cells play a dominant role over other lymphocyte populations in providing the cytokine environment for regulating macrophages towards an M2 profile under normal wild-type conditions.