No effect of mAbp1 on β₂ integrin expression, up-regulation, and localization during phagocytosis or fibrinogen binding. (A) Flow cytometric analysis of cell-surface expression of GR-1, CD11b, and CD18 in mAbp1^+/+ or mAbp1^−/− PMNs stimulated with KC (100 ng/mL), TNFα (100 ng/mL), or left unstimulated. (B) Confocal microscopy images of murine PMNs phagocytosing serum-opsonized Alexa 594–conjugated E coli (red). Translocation of CD18 (green) to the site of particle binding (arrows) was not affected in Abp1^−/− PMNs. Bar = 10 μm. Data are representative for 3 independent experiments. (C) Binding of Alexa 488–conjugated fibrinogen to murine mAbp1^+/+ and mAbp1^−/− PMNs as measured by flow cytometry. Cells were incubated for 20 minutes with EDTA as negative control, Mn²⁺ (3 mM), TNFα (100 ng/mL), or left unstimulated. Addition of 1 mM Mn²⁺ gave similar results (data not shown). Mean fluorescence intensity within marker 1 (M1) ± SD; n = 4; #P < .05 versus unstimulated control; n.s. indicates not significant versus wild-type control.