CD8A and HIV infectious disease: In addition to elevated T-cell turnover and an increase in the proportion of highly differentiated antigen-experienced CD8+ and CD4+ T-cells during HIV infection (Wolthers et al. 1996b; Appay et al. 2002c), HIV-infected individuals are characterised by decreased thymic output (Douek et al. 1998) and reduced naïve T-cell numbers (Roederer et al. 1995; Hellerstein et al. 1999, Hellerstein et al. 2003), which reflect a diminished capacity to renew the pool of T-cells.