MSCs inhibit IFN-γ secretion from purified NK cells. Natural killer cells were purified and cocultured with hMSCs for different times in the presence of rhIL-2. The levels of IFN-γ in the supernatant were quantified in the presence or absence of hMSCs after 24 hours of coculture. The bars show the percent change in IFN-γ secreted compared with IL-2-stimulated NK cells (= 100%). When hMSCs were present, there was a more than 80% decrease in levels of IFN-γ secreted by IL-2-stimulated NK cells. Results from 3 independent hMSC/NK experiments are plotted. Error bars represent mean ± SD.