A RAPID ACTIVATION ASSAY FOR HUMAN EOSINOPHILS BASED ON ADHESION TO IMMOBILIZED ICAM-1, VCAM-1 AND IGG

Interleukin 5 (IL-5) is a T-cell derived cytokine that induces eosinop hil growth and differentiation in both mouse and human bone marrow cul tures. Elevated levels of IL-5 as well as eosinophils have been detect ed in the sputum and bronchoalveolar lavage (BAL) fluids of asthmatics . Since the recruitment of inflammatory cells to tissues requires the participation of adhesion molecules, we have developed a rapid and sen sitive assay to examine the effect of IL-5 and other activation stimul i on eosinophil adhesion to recombinant intercellular adhesion molecul e-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1). Human re combinant IL-5, granulocyte-macrophage colony stimulating factor (GM-C SF), interleukin 3 (IL-3), tumour necrosis factor alpha (TNF-alpha), R ANTES, MCP-3, C5a, PAF, fMLP, PMA and ConA all induced adhesion of pur ified eosinophils obtained from normal donors to ICAM-1 and VCAM-1 in a dose and time dependent manner, Adhesion was rapid, within 15 minute s of culture at 37 degrees C, and plateaued within 30 minutes. Activat ed eosinophils also adhered rapidly to immobilized IgG via the type II Fc gamma receptor (CD32). Analysis of the effect of IL-5 on surface m olecule expression by FACS analysis revealed increased expression of C D11b molecules and decreased expression of L-selectin, but no change i n the expression of CD11a, CD18, CD29, CD49d and CD32, We also show th at Mac-1 plays an important role in the regulation of eosinophil activ ation, since antibodies to CD11b can block IL-5 induced adhesion to Ig G and IL-5 induced degranulation.