Characterization of T Cell Subsets Involved in the Production of IFN-gamma in Asymptomatic HIV-Infected Patients.

Cells capable of interferon (IFN)-γ synthesis following mitogenic stimulation can be detected and quantified by a recently developed immunofluorescence assay and flow cytometric analysis. The production of IFN- γ was investigated in a cohort of 20 asymptomatic human immunodeficiency virus (HIV)-seropositive patients with normal numbers of CD4+ lymphocytes, and in 10 healthy subjects. About 60% of asymptomatic stage A1 patients had increased percentages of blood lymphocytes capable of IFN-γ synthesis, as compared to healthy subjects. The difference reflected the relatively higher numbers of CD8+ cells, in particular the CD8+ T cell subset lacking CD28 antigen expression. The strong correlation between the CD4+/CD8+ ratio and the CD8+CD28+/CD8+CD28- ratio suggests either a role for CD4+ cells in controlling the CD28+ phenotype or a role for CD8+CD28- cells in the decline of CD4+ lymphocytes. The peculiar ability of CD8+CD28- cells to produce high amounts of IFN-γ, as compared to CD8+CD28+ cells, supports the hypothesis that the CD8+CD28- lymphocytes constitute a population that is functionally distinct from their double-positive counterparts.