T cells are a major component of the adipose tissue milieu, and while the enrichment of CD8+ T cells appears broadly similar in obesity and HIV infection, differences in CD4+ T cells and, likely, macrophage populations suggest that the stimuli driving CD8+ cell enrichment and the interactions of CD8+ cells with other immune cells differs between the two conditions. The gene discussed is CD8A; the disease is obesity due to melanocortin 4 receptor deficiency.