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.