Verdict in the case of therapies versus eosinophils: the jury is still out.

Eosinophils are regarded by many as fundamental to the pathophysiology of allergic diseases, including asthma. An improved understanding of the mechanisms involved in these responses is therefore of great relevance to asthma pathogenesis and the development of new therapeutics. Most therapies that are effective in reducing allergic inflammation in animals and human subjects diminish tissue eosinophilia and levels of eosinophil-derived mediators. However, recent efforts with more selective eosinophil-suppressive therapies have failed to affect disease, bringing into question the role of eosinophils in asthma. This article will provide a brief overview of the role of eosinophils in allergic diseases, followed by a discussion of both eosinophil-specific and eosinophil-selective therapeutic targets, with a focus on cell-surface molecules. The known and theoretic benefits and risks of these strategies will also be covered.