Competitive-binding studies by flow cytometry and effect of anti-Mart on respiratory burst activity of neutrophils. (A) U937 cells were incubated with mAb LPM-19c directed against the I domain of CD11b or with IgG from anti-Mart (serum 1) in the absence (blue) or in the presence of I domain (red). Gray histograms represent the isotype control. Bound antibodies were detected with fluorescein-labeled secondary antibodies. (B) U937 cells were incubated with anti-Mart IgG from serum 1 (red) or serum 2 (green) in the absence (top) or presence (bottom) of mAb CBRM1/32. Bound human IgG was detected with fluorescein-labeled secondary antibodies. (C) Neutrophils were incubated with control IgG (black line), mAb 7D8 against CD177 (blue), or IgG fractions derived from anti-Mart sera 1 and 2. ROS production after stimulation with fMLP was measured using flow cytometry. Filled histogram represents unstimulated control without fMLP. All sets of histograms represent the results of 1 of 3 separate experiments.