CD4 and AIDS: In the very first description of AIDS in 1981, the authors described a new acquired severe immune deficiency that was characterized by a loss of CD4+ T-cells (Leu 3+), a concomitant increase in CD8+ T-cells (Leu 2+), resulting in a low CD4:CD8 T-cell (Leu3+/Leu2+) ratio, and a severe loss of CD3+ T-cell (Leu 1+) homeostasis [3].