[The immunologic role of eosinophilic granulocytes within the scope of inflammatory lung diseases]

Although identified over a hundred years ago, the precise role of the eosinophil in eosinophil-associated diseases still remains undefined. However, the results of modern cellular, immunological, and biochemical investigations have suggested that eosinophils contain unique constituents and functional adaptions through which eosinophils gain a profound cytotoxic capacity. This property may not only be crucial for the host defence mechanism against helminthic infections but may also be involved in the pathogenesis of chronic inflammation associated with allergic reaction and other eosinophilic disorders. There is increasing evidence available that the eosinophil may cause damage to host tissue and elicit tissue fibrosis. The eosinophil appears to adapt certain general cellular characteristics during its ontogeny and participation in inflammatory reactions, such as hypodensity, expression and induction of surface markers and adhesion molecules. In addition, there is evidence that the eosinophil may undergo a shift between hypo- and hyperreactivity states. Factors regulating the level of eosinophil activation may include both lipid mediators and cytokines released by macrophages, mast cells, platelets, endothelial cells, and T lymphocytes. The rapidly evolving understanding of the functional properties of the eosinophil will further help to define the pathogenesis of certain eosinophilic disorders and may provide the basis for new therapeutic strategies in eosinophilic disorders.