Inhibition of M112 MoAb binding by IL-15. MONO-MAC-6 cells were preincubated for 30 minutes at 4°C with medium (A), 0.01 μg (B), 0.1 μg (C), 1 μg (D), or 10 μg (E) of human recombinant IL-15 and then stained with M112 MoAb as described in Fig 1. Open histograms with a bold line represent M112 staining; open histograms with a gray line represent the residual staining after preincubation with IL-15; and solid histograms refer to the background fluorescence.