Similarly to the studies of B cells noted above (see Section 2.3.1), immune senescence of CD8+ T cells is mediated in part by age-related reductions in autophagy, and spermidine supplementation can induce autophagy, increase antigen-specific CD8+ T cells, and improve the CD8+ T cell responses to vaccination and to infections in old mice [35]. The gene discussed is CD8A; the disease is infection.