Cross-linking of the β₂ integrin, CD11b/CD18, on human eosinophils induces protein tyrosine phosphorylation and cellular degranulation

Adhesion molecules, including integrins, play an important role in the selective recruitment of eosinophils. It has recently been shown that integrins also modulate the functions of eosinophils. Here, we tested the hypothesis that cross-linking of the β₂ integrin, α(M)β₂ (Mac-1, CD11b/CD18), leads to intracellular signaling events such as activation of protein tyrosine kinases leading to eosinophil degranulation. Cross-linking of cell surface CD11b/CD18 with anti-CD11b antibody and goat anti-mouse IgG immobilized onto the plate triggered tyrosine phosphorylation of several intracellular proteins, including the one with a 115-kD molecular mass (pp115). The same stimulus also provoked degranulation of eosinophils. These findings suggest that engagement of β₂ integrin on eosinophils triggers the activation of intracellular signaling cascade which leads to cellular degranulation.