Early on in the AIDS pandemic and before identification of the etiologic virus, Landay and colleagues (1) as well as Nicholson et al. (2) demonstrated that a deficiency of CD4+ T cells and an inverted CD4:CD8 ratio were present in asymptomatic hemophiliac individuals and in men who have sex with men (MSM) with lymphadenopathy. The gene discussed is CD4; the disease is AIDS.