CROSS-LINKING OF THE BETA(2) 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 r:hat cross-linking of the beta(2) integrin, alpha(M)b eta(2) (Mac-1, CD11b/CD18), leads to intracellular signaling events su ch as activation of protein tyrosine kinases leading to eosinophil deg ranulation. Cross-linking of cell surface CD11b/CD18 with anti-CD11b a ntibody and goat anti-mouse IgG immobilized onto the plate triggered t yrosine phosphorylation of several intracellular proteins, including t he one with a 115-kD molecular mass (pp115). The same stimulus also pr ovoked degranulation of eosinophils. These findings suggest that engag ement of beta(2) integrin on eosinophils triggers the activation of in tracellular signaling cascade which leads to cellular degranulation.