CD4 and HIV infectious disease: Untreated HIV infection is characterized by a derangement of the immune system, with reductions in the CD4+ T cell count, increases in the CD8+ T cell count, and an abnormally low CD4+:CD8+ T cell ratio,1 as well as increased levels of inflammatory markers, with changes occurring soon after seroconversion.2 Treatment with combination antiretroviral therapy (cART) generally results in rapid suppression of HIV viremia and improvements in immune markers—however, in some individuals, immune markers remain abnormal, despite viral suppression.