Eosinophil Apoptosis

University dissertation from Uppsala University Library

Abstract: Apoptosis or programmed cell death is crucial for the resolution of inflammation, and phagocytosis of apoptotic cells initiates the release of actively anti-inflammatory responses from the phagocytes. Eosinophils are one of the most potent inflammatory cells in the body and is involved in a number of diseases, most commonly associated with parasitic infections and allergic diseases. Apoptosis in eosinophils is therefore one of the most important systems to avoid inflammation. This aim of the present investigation was to examine the mechanisms behind, and the consequences of this process in eosinophils. Apoptotic eosinophils have a unique surface receptor expression that indicates abilities to communicate with T-, B- and antigen presenting cells. They have a novel expression of CD49f, indicating an importance for binding to laminin or unknown functions of the VLA-6 receptor, possibly in the concept of phagocytosis of the apoptotic cell. In apoptotic eosinophils the granules are translocated to the periphery of the cell, probably through a disruption of the cytoskeleton. This translocation makes the granules easily accessible and the apoptotic eosinophil can release considerable amounts of granule proteins in response to specific stimuli. The spontaneous release however, is decreased as compared with living cells. Furthermore, the survival of eosinophils in response to an allergen challenge is increased in healthy subjects, but not in allergic patients. Mechanistically, this needs further investigation, but one theory is that it is due to the presence of specific IgE in patients in combination with differences in the response from the epithelial cells.