CD4 and HIV infectious disease: A CD4:CD8 T-lymphocyte ratio less than 1.0 is associated with HIV infection and has been proposed as a parameter for the diagnosis of HIV in African children under 18 months old,32 where results of HIV rapid tests can be complicated by maternal antibody to HIV.10,32 With decreased CD4+ and increased CD8+ T-lymphocyte concentrations in young children in this study compared with results from developed countries, 13% of Malawian children under 18 months had a CD4:CD8 ratio <1.0.