Expression of α_Dβ₂ and α_Mβ₂ on the surface of IC-21 macrophage cell line and their role in macrophage migration. (A) The level of α_Dβ₂ and α_Mβ₂ expression was assessed by flow cytometry with mAb 1/70, which recognizes mouse α_Mβ₂, and polyclonal anti-α_D antibody, which recognizes both human and mouse α_D integrin subunits. Control cells are shown as open histograms. (B) IC-21 cells were analyzed for their ability to migrate to 10 μg/mL vitronectin either in the absence or in the presence of blocking polyclonal anti-α_D and anti-α_M mAb M1/70. Cells were preincubated with 2.5 μg/mL of each antibody for 20 minutes before their addition to the upper chamber of Transwell plates. In control samples, cells were pretreated with 2.5 μg/mL of each rabbit or rat IgG. Cells were allowed to migrate toward vitronectin for 18 hours at 37°C and the extent of cell migration was assessed as described in “Materials and methods.”