Abnormal intracellular IL-2 and interferon-gamma (IFN-γ) production as HIV-1-associated markers of immune dysfunction

We used three-colour cytometry to analyse intracellular cytokine production in activated whole blood cultures derived from patients with HIV-1 infection. We assessed mitogen-induced IL-2, IL-4 and IFN-γ production from T cells as possible markers of immune dysfunction. The percentages of T cells staining for IL-2 were significantly reduced in stimulated cultures from HIV⁺ individuals relative to normal controls (P < 0.0001); this reduction was observed in both the CD4⁺ and the CD8⁺ subsets. IL-2 production was significantly reduced in CD4⁺ T cells from HIV⁺ individuals clinically classified as symptomatics compared with HIV⁺ asymptomatics (P < 0.001); in addition, production of IL-2 inversely correlated with viral load (r² = 0.832). On the other hand, HIV⁺ individuals showed significantly more T cells staining positive for IFN-γ (P < 0.0001); subset analysis identified these T cells as CD8⁺. Increased IFN-γ production in the CD8⁺ T cell subset of HIV⁺ individuals correlated neither with clinical status nor with plasma viral load. IL-4 staining in activated T cells was low (< 5%) and no differences were observed between HIV⁺ and control groups. Three-colour FACS analysis of whole blood provides a sensitive, rapid and relatively easy means to detect cytokine profiles within T cell subpopulations. Only small volumes of blood are required (0.5 ml), since there is no need for cell isolation, making it more practical than ELISA or reverse transcriptase-polymerase chain reaction (RT-PCR) for the analysis of immune function in HIV⁺ individuals. This technique could therefore play a role in mapping the dynamics and extent of immune recovery in AIDS patients undergoing triple combination therapy.