CD8A and obesity due to melanocortin 4 receptor deficiency: In contrast with obesity, the pro-inflammatory cytokine-producing T helper type 1 (TH1) cells, CD8+ cytotoxic T cells, and NK cells that produce IFNγ (Kammoun et al., 2014; Deng et al., 2016) become abundant in the adipose tissue due to excess leptin, which leads to M1 macrophage accumulation and polarization (Deng et al., 2016).