CD4 and HIV infectious disease: Outside HIV infection, a low CD4/CD8 ratio, namely the immune risk profile, has been proposed as a surrogate marker of the collection of immune-related defects that defines “immunosenescence” –a phenomenon characterized by the T-cell proliferation and differentiation resulting in the generation of antigen experienced, highly differentiated and dysfunctional T-cells [13]– and correlated with all-cause mortality in the elderly [18]–[20], [35].