IL6 and obesity due to melanocortin 4 receptor deficiency: Xia, et al. [63] report that Gr-1+CD11b+ cells accumulate in the adipose of genetically obese (ob/ob) tumor-free animals in comparison to wild-type controls, and improve insulin sensitivity and reduce serum IL-6, suggesting that MDSCs may be negative regulators of obesity-induced inflammation in the absence of tumor.