Ligand binding to Mac-1 is required for the formation of Mac-1 clusters and F-actin patches in PMNLs challenged with P-selectin.

PMNLs, preincubated for 10 minutes at 4°C with 20 μg/mL control antibody (A-C) or anti-CD18 antibody IB4 (G-I) were challenged with 10 μg/mL P-selectin–IgG chimera. Alternatively, PMNLs were challenged with 10 μg/mL P-selectin–IgG chimera preincubated for 10 minutes with 20 μg/mL anti–P-selectin antibody, WAPS (D-F). Incubation in standard conditions was stopped at 2 minutes, and samples were processed for confocal laser scanning microscopy. A, B, and C show an aggregate of 4 cells. A, D, and G show F-actin staining, and B, E, and H show CD11b staining. In the overlay (C, F, I), yellow represents colocalization of the 2 stainings. The figure reports the results from a representative of 3 different experiments.