DERMAL EOSINOPHILS IN ATOPIC-DERMATITIS UNDERGO CYTOLYTIC DEGENERATION

Background: Immunofluorescent staining for eosinophil granule proteins in lesional skin of patients with atopic dermatitis shows extensive e xtracellular deposition throughout the upper dermis with relatively fe w intact eosinophils, Objective: This study was carried out to determi ne whether eosinophil granule protein deposition in atopic dermatitis occurs by classical exocytosis, by piecemeal degranulation, or as a re sult of cytolysis. Methods: Skin biopsy specimens from 10 patients vii th atopic dermatitis were examined by electron microscopy. Results: Th e biopsy specimens showed varying degrees of dermal eosinophil granule major basic protein deposition by indirect immunofluorescence, Specim ens from seven patients showed striking alterations of eosinophils by electron microscopy including intact eosinophils with granule alterati ons (reversal of core staining and/or core lucency) and with uropod pr ocesses. Biopsy specimens from six patients showed evidence of eosinop hil degeneration with disruption of nuclear and/or plasma membranes. I n four patients' specimens, membrane-bound eosinophil granules were pr esent near degenerating eosinophils or were present in the absence of recognizable eosinophils, Evidence of classical exocytotic degranulati on was not observed, Two of the specimens were also examined by immuno electron microscopy for major basic protein localization, In these, ma jor basic protein appeared to be lost from the granule core and distri buted in the eosinophil cytoplasm as granules disintegrated and the ce ll disrupted. Conclusion: These findings support the hypothesis that e osinophils undergo cytolysis with release of granule contents and memb rane-bound granules; this is likely the usual mechanism of eosinophil granule protein release in atopic dermatitis.