CD8A and obesity due to melanocortin 4 receptor deficiency: Combined, these findings suggest that the functional defects in CD8 T cells in tumors of obese mice are not a consequence of increased immune checkpoint expression in the tumor microenvironment (TME); rather, they suggest that obesity promotes an “immune-cold” tumor phenotype through mechanisms other than accelerating immune checkpoint–driven T cell exhaustion (Bindea et al., 2014).