Adhesion of activated eosinophils to respiratory epithelial cells is enhanced by tumor necrosis factor-alpha and interleukin-1 beta.


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Abstract

Eosinophilic infiltration and damage to airway epithelium are characteristic features of asthma. To assess possible interactions between eosinophils and airway epithelium, Percoll-purified human peripheral blood eosinophils were evaluated for their ability to adhere to respiratory epithelial cell (REC) cultures. REC (an immortalized cell line, A549, and primary bronchial epithelial cells) were grown in 96-well tissue culture plates, treated with proinflammatory cytokines (TNF-alpha or IL-1 beta), and eosinophil adhesion to these tissues was determined. Cytokine treatment of the REC cultures significantly increased expression of intercellular adhesion molecule-1 (ICAM-1) (P < 0.01). Eosinophils demonstrated a variable baseline adhesion to untreated REC which was then significantly increased following activation with phorbol myristate acetate (PMA) (P < 0.01). Furthermore, treatment of REC monolayers with TNF-alpha or IL-1 beta significantly increased adhesion of PMA-stimulated eosinophils (P < 0.01). To delineate the adhesion proteins involved in the cell-cell interactions, assays were performed in the presence of specific blocking monoclonal antibodies to eosinophil CD18, CD11a, or CD11b, and REC ICAM-1 molecules. Blocking antibodies to ICAM-1 had no significant effect on levels of eosinophil adhesion. In contrast, antibodies to CD18, CD11a, and CD11b significantly decreased (P < 0.01) eosinophil adhesion, thus demonstrating pivotal roles for the CD11/CD18 (beta 2) integrins, but not necessarily for ICAM-1, in interactions between the REC and eosinophils. These data demonstrate that TNF-alpha and IL-1 beta increase eosinophil adhesion to human respiratory epithelial cell cultures by induction of ligands recognized by eosinophil beta 2 integrins.

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