PRODUCTION OF IL-10 BY HUMAN NATURAL-KILLER-CELLS STIMULATED WITH IL-2 AND OR IL-12/

Human NK cell activity can be augmented in vitro by stimulation with I L-2 or IL-12, both of which also induce the production of IFN-gamma, T NF-alpha, and granulocyte-macrophage CSF by NK cells, For the first ti me, we demonstrate that freshly purified NK cells stimulated with IL-2 proliferated and produced IL-10 in a dose-dependent manner, IL-10 mRN A expression, as detected by semiquantitative reverse transcription-PC R, reached peak levels at 24 h, IL-10 protein was detectable on day 2 and further increased on days 3 and 6 as measured by ELISA, However, I L-12 alone induced neither substantial proliferation nor detectable IL -10 production by fresh NK cells, but it synergized with IL-2 in induc ing IL-10 mRNA expression and protein synthesis, IL-10 production by a ctivated NK cells was confirmed by intracytoplasmic cytokine staining by three-color immunofluorescence of CD16(+) and/or CD56(+) NK cells w ith anti-IL-10 antibody, IL-10 production by NK cells was further conf irmed in the NK-like cell line, YT, which constitutively expressed IL- 10 mRNA and protein, IL-12 alone did not induce NK proliferation, but it inhibited IL-2-induced proliferation, Neutralization of endogenousl y produced IL-10 with anti-IL-10 antibodies did not overcome the inhib ition of IL-2-induced proliferation by IL-12. Together, these results demonstrate that IL-2 and IL-12 synergize to induce IL-10 production b y human NK cells and that IL-12 inhibits IL-2 induced NK cell prolifer ation by an IL-10-independent mechanism.