Tissue eosinophilia and local deposition of eosinophil granule proteins: Regulation and significance in the inflammatory response of atopic dermatitis and other inflammatory skin diseases

Recent in vitro-studies have substantially increased our knowledge of eosinophil activation,the regulation of eosinophilia in the peripheral blood and the role of cytokines in that process. Accordingly, chemoattraction and activation of eosinophils by cytokines results in the local release of reactive oxygen species and toxic cationic granule proteins followed by local propagation of the inflammatory reaction and tissue damage. This extracellular tissue deposition of toxic granule proteins as an expression of complete activation of eosinophils, rather than only the presence of intact eosinophil granulocytes, is crucial for their functional effect in situ. Semiquantitative studies of local eosinophil granule deposition so far have been done only in atopic dermatitis and a limited number of other inflammatory skin diseases as summarized in this review. Evaluation of the pathogenetic role of eosinophils may be of potential therapeutic importance.