CD4 and obesity due to melanocortin 4 receptor deficiency: Interestingly, adoptive transfer of CD4+ cells especially Th2 CD4+ T cells, which produce IL-4 and IL-13, rescues HFD-induced obesity and insulin resistance in Rag1 deficient mice suggesting that Th2 cytokines such as IL-4 and IL-13 suppress HFD-induced inflammation to improve insulin sensitivity (Winer et al., 2009a).