Granulocyte macrophage colony-stimulating factor augments ICAM-1 and VCAM-1 activation of eosinophil function

Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) are members of the immunoglobulin superfamily adhesion molecules on vascular endothelium and important in the development of eosinophil (EOS) accumulation in allergic inflammation. To define the role of these adhesion proteins in EOS inflammation, peripheral blood EOS from allergic donors were incubated in either buffer (control)-, recombinant human (rh)-VCAM-1-, or rh-ICAM-1-coated plates, and the effects of these adhesion proteins on EOS effector functions were determined. VCAM-1 induced spontaneous EOS adhesion whereas EOS adhesion to ICAM-1 required a second signal, such as granulocyte macrophage colony-stimulating factor (GM-CSF). Although only VCAM-1 stimulated EOS superoxide anion (O₂) generation, the addition of GM-CSF (100 pM) to the reactions resulted in a greater and equivalent production of O₂ with VCAM-1 and ICAM-1. In the presence of GM-CSE, ICAM-1 and VCAM-1 caused significant release of EOS-derived neurotoxin (EDN). Moreover, only ICAM-1 (no GM-CSF) promoted calcium ionophore A23187 (0.2 μM)-induced EOS leukotriene C₄ (LTC₄). Enhanced O₂ generation, EDN release, and LTC₄ generation observed with ICAM-1 and VCAM-1 were significantly inhibited by anti-β₂-integrin antibody. These results suggest that ICAM-1 and VCAM-1 are important in determining the eventual function of airway EOS.