Epithelial injury by human eosinophils.

The human eosinophil is armed with a number of very potent cytotoxic granule proteins that upon extracellular release may produce considerable damage. The toxic effect of the proteins seems to be quite unselective, involving most mammalian and nonmammalian cells including the epithelial cells. The demonstration of a close relation between the deposition of eosinophil granule proteins and areas of epithelial cell destruction in a variety of diseases including asthma and the fact that cytotoxic concentrations of the proteins have been measured in the fluid phase suggest that the eosinophil participates actively in the pathogenesis of airway diseases. The protection towards the adverse actions of the eosinophil, particularly towards their proteins, therefore seems vital. The discovery of alpha-2-macroglobulin as a specific binder of eosinophil cationic protein may be relevant in this regard.