While the number of CD4+-T-cells in the peripheral blood has originally been linked to a high risk for the development of acquired immunodeficiency syndrome (AIDS) in HIV-infected patients and is used as a marker for stages in AIDS (24, 25), reduced CD4+-T-cells have also been shown to be a marker for the risk of PcP in non-HIV-infected patients (26, 27). The gene discussed is CD4; the disease is AIDS.