Defective T-cell colony formation and IL-2 receptor expression at all stages of HIV infection

The T-cell colony assay is a highly sensitive measure of immunological dysfunction. The present study evaluated this in vitro response in asymptomatic HIV-infected homosexuals, those with chronic adenopathy as their only clinical manifestation and patients with either ARC or AIDS. The mean colony count in antibody-positive asymptomatic individuals was significantly reduced when compared to either heterosexual controls or antibody-negative homosexuals. Furthermore, there were no differences in the responses of these antibody-positive individuals and those with chronic lymphadenopathy as their only clinical manifestation. By contrast, patients with AIDS or ARC showed a profound defect; this suggests that the colony assay can detect a functional gradient across the spectrum of HIV infections. Colony growth was correlated with the absolute number of T-helper cells and the ability of PHA-stimulated lymphocytes to express IL-2 receptors; no correlation was found with the number of suppressor/cytotoxic cells or in vitro production of IL-2. Recent HIV seroconverters had normal colony counts but impaired ability to express IL-2 receptors. These data suggest a sequential loss of T-cell function as a result of HIV infection; the earliest manifestations are impaired expression of IL-2 receptors and reduced proliferative responses, as measured in the colony assay.