Transmission electron micrographs of human tissue eosinophils from (A) allergic and (B) hypereosinophilic patients. Biopsy samples from the left frontal sinus and the skin were obtained from a patient with allergic sinusitis and a patient with hypereosinophilic syndrome (negative for FIP1-like 1/platelet-derived growth factor-α mutation), respectively. In (Ai), a biopsy of the frontal sinus shows infiltrated eosinophils. Note the disrupting nuclei (Nu) and extracellular free secretory granules. (Aii) is the boxed area of (Ai) seen at higher magnification. In (B), both free granules (Gr) and disrupted nuclei (Nu) are also observed in eosinophils from a skin biopsy. Arrowheads in (Aii) and (B) indicate releasing decondensed chromatin. Samples were fixed in a mixture of glutaraldehyde and PFO and prepared for conventional TEM as in “Materials and methods.” Scale bars represent 1.2µm (Ai), 700 nm (Aii), 600 nm (B).