Abstract
Peripheral blood eosinophils from two normal donors and two patients with the hypereosinophilic syndrome (HES) were analyzed with a post-embedding immunogold method to detect the substructural location of tumor necrosis factor-alpha (TNF-alpha). In eosinophils of HES patients, TNF-alpha was localized to the matrix compartment of 64% of the specific secondary granules. Other structures in the HES eosinophils were unlabeled. No TNF-alpha was detected in eosinophils of normal donors. These studies document the first ultrastructural subcellular localization of any cytokine within the major population of secretory granules in human eosinophils and support other lines of evidence indicating that the expression of TNF-alpha may be greater in the eosinophils of HES patients than in those of normal donors.