During healthy aging, CD4+ and CD8+ T-cell numbers remain relatively stable, despite a significant decline in thymus output. This T-cell homeostasis is dramatically disturbed during HIV infection, during which naive and memory CD4+ and naive CD8+ T-cell numbers gradually decline, eventually leading to increased susceptibility to opportunistic infections. In contrast, memory CD8+ T-cell numbers are significantly increased in HIV infection. Although the causes of disturbed lymphocyte homeostasis in HIV infection have been subject of much debate, there is a current consensus that the deleterious effects of chronic immune activation play a central role.
During effective combination antiretroviral therapy (cART), CD4+ T-cell numbers tend to come back to healthy control levels, albeit very slowly, while memory CD8+T-cell numbers tend to remain elevated for long periods of time. It remains unclear whether active homeostatic mechanisms kick in to reestablish lymphocyte homeostasis...