Human Eosinophils Express Functional Interleukin 2 Receptors

Because T cell-derived cytokines may affect the functioning of eosinophils, we have investigated the capacity ofhuman eosino-phils to respond to IL-2. IL-2 was a potent chemoattractant with EDI0 of 10-12 M with eosinophils from all normal and eosinophilic donors tested. The monoclonal antibodies anti-Tac and TU27 against p55 (Tac/CD25) and p75 receptor subunits, respectively, each inhibited IL-2-dependent eosinophil migra-tion. The molar potency of IL-2 and the inhibitory activity of each of the above antibodies suggest that high affinity heterodi-meric IL-2 receptor complexes mediated the migration re-sponses of eosinophils to IL-2. Binding of monoclonal antibody against p75 was not detectable by flow cytometry, and high affinity binding sites for "25I-IL-2 were below the limits ofquan-titation on eosinophils from individuals with eosinophilia. Ex-pression of p55 (Tac/CD25) by eosinophils, without require-ment for in vitro activation, was demonstrable by flow cytome-try, radioimmunoprecipitation, and Northern blotting for mRNA. Surface expression of p55 on eosinophils from normal or eosinophilic individuals increased during culture for 24-48 h with a biologic activity purified from stimulated U937 cells and to a lesser extent with granulocyte-macrophage CSF or lym-phocyte chemoattractant factor but not with nine other cyto-kines. These studies indicate that blood eosinophils respond to IL-2 and identify one mechanism whereby activation ofT lym-phocytes may influence the function of eosinophils. (J. Clin. Invest. 1991. 88:825-832.) Key words: adult T cell leukemia-derived factor * chemotaxis- eosinophil cytotoxicity-enhancing factor * granulocyte * lymphocyte chemoattractant facto