Eotaxin induces a sustained reduction in the functional adhesive state of very late antigen 4 for the connecting segment 1 region of fibronectin

Background: Eosinophils that have bound to extracellular matrix proteins, s uch as the connecting segment 1(CS-1) region of fibronectin, need to deadhe re before undergoing chemotaxis through the extracellular matrix. Objective: We have investigated whether eotaxin can regulate the strength o f eosinophil adhesion to the CS-I region of fibronectin. Methods: We have used a micropipette single-cell adhesion assay to determin e the force of eosinophil adhesion to the CS-I region of fibronectin. Results: Eosinophils bound to CS-1 with high avidity, and this binding coul d be inhibited with neutralizing antibodies to alpha4 integrins expressed b y eosinophils or with neutralizing antibodies to CS-l, Eosinophils incubate d in the presence of eotaxin demonstrated a transient increase in the force of eosinophil adhesion to CS-1, which was followed by a more sustained red uction in the force of eosinophil adhesion to CS-1, as assessed in the micr opipette single-cell adhesion assay. This decreased binding of eosinophils to CS-I was not due to alterations in very late antigen 4 (VLA-4) receptor number, as assessed with FACS analysis, or alterations in VLA-4 receptor di stribution, as assessed with immunofluorescence microscopy. Conclusions: These studies suggest that eotaxin can cause a transient incre ase followed by a more sustained reduction in the functional force of VLA-4 adhesion to CS-I and thus promote deadhesion of CS-l adherent eosinophils in the extracellular matrix.