Differential production of IFN-gamma, analyzed at the single-cell level, by specific subsets of human NK and T cells from healthy and HIV+ subjects

Background: Interferon gamma is a cytokine that plays a central role in imm unity, and is physiologically secreted by T and NK cells under appropriate stimuli during the immune response. By means of flow cytometry, we performe d a single cell, analysis of interferon gamma producing NK cells and their surface phenotype in normal and HIV+ individuals that show several defects of cytokine production and cellular immunity. Methods: PBMC or purified NK cells were stimulated for 1-12 h with PMA/iono mycin in the presence of monensin, subsequently stained for surface CD56 an d CD3 or CD8, and for intracptoplasmic IFN-gamma, and analysed by how cytom etry. Results: Our results show that CD56(+) NK cells are more efficient interfer on gamma producers than T cells. Moreover, within the CD56(+) NK cell popul ation, those that co-express low density CD8 are the best producers. Finall y, we show that NK cells during HIV infection are more massively recruited to interferon gamma production than those from normal subjects. Conclusions: Both in the normal and HIV+ subjects, a higher percentage of N K cells than T cells can produce IFN-gamma although differences can be iden tified within the NK cells subset in terms of IFN-gamma production. The pro duction of IFN-gamma is fully achievable in the HIV+ subjects, which is con sistent with their elevated plasmatic levels of the cytokine. The possibili ty that NK cells that produce interferon gamma could represent a functional ly distinct population committed to the production of this cytokine, is dis cussed. (C) 2000 Wiley-Liss, Inc.