Figure 2.

Schematic of stepwise effect of chronic inflammation and MDSC and M2 macrophages in the setting of obesity. In normal (non-obese) state, few macrophages are associated with fat cells in adipose tissues, with minimal inflammation. During early obesity, more macrophages are recruited. These cells produce pro-inflammatory cytokines, in a M1 macrophage inflammatory response pattern. As obesity progresses, insulin resistance develops. A physiologic as well as immune response to this chronic insulin resistance and chronic inflammation is the induction of the M2 macrophage response.