PROSTAGLANDIN ENDOPEROXIDE SYNTHASE (CYCLOOXYGENASE) - ULTRASTRUCTURAL-LOCALIZATION TO NONMEMBRANE-BOUND CYTOPLASMIC LIPID BODIES IN HUMAN EOSINOPHILS AND 3T3 FIBROBLASTS

Lipid bodies are nonmembrane-bound cytoplasmic inclusions which are pr ominent in cells engaged in inflammatory responses. Using postembeddin g immunogold localization with a primary anti-PGH (prostaglandin endop eroxide) synthase monoclonal antibody, PGH synthase was localized by e lectron microscopy to lipid bodies of two prostaglandin-forming cells: human eosinophils and murine 3T3 fibroblasts. Freshly isolated eosino phils from a hypereosinophilic syndrome donor and peripheral blood eos inophils maintained in coculture with 3T3 fibroblasts and granulocyte- macrophage colony-stimulating factor were studied. In both cell types, lipid bodies were the predominant structures labeled with anti-PGH sy nthase. Labeling was absent in controls. In both human eosinophils and murine fibroblasts, lipid bodies represent sites of localization of P GH synthase the rate-limiting initial enzyme in the formation of prost aglandins - and may serve as specific sites of formation of cyclooxyge nase-pathway-derived eicosanoids.