Intriguingly, they also demonstrated that compared with the lean controls, AT derived from mice fed on an HFD elevated the proliferation of cocultured splenic CD8+ T cells in vitro, indicating that AT CD8+ T cells might clonally expand in obesity, which suggests a crucial mechanism through which obesity induces the inflation of CD8+ T cells in adipose tissue. The gene discussed is CD8A; the disease is obesity due to melanocortin 4 receptor deficiency.