Accrual of killer CD4 T cells has been implicated as a disease mechanism in cardiovascular disease, where CD4 T cells can lyse both endothelial cells and vascular smooth muscle cells (Pryshchep et al., 2006; Sato et al., 2006), laying the ground for the immune-mediated damage of blood vessels, the major cause of age-related morbidity and mortality (Figure 2). This evidence concerns the gene CD4 and cardiovascular disorder.