Ultrastructural localization of Charcot-Leyden crystal protein (lysophospholipase) and peroxidase in macrophages, eosinophils, and extracellular matrix of the skin in the hypereosinophilic syndrome.

Electron microscopy, ultrastructural cytochemistry, and postembedding immunogold ultrastructural immunocytochemistry were used to study a papular cutaneous lesion from a patient with the hypereosinophilic syndrome. Peroxidase activity was detected cytochemically in 40-microns sections of skin utilizing the substrate diaminobenzidine; Charcot-Leyden crystal (CLC) protein was detected immunocytochemically in skin utilizing a postembedding immunogold technique; and a combined method was used where postembedding immunogold staining of CLC protein was performed on sections previously prepared to detect peroxidase activity. We describe a unique, eosinophil-rich inflammatory process in involved skin which contained extraordinary numbers of morphologically activated macrophages. Electron microscopy demonstrated (a) widespread eosinophil necrosis, (b) interstitial CLC formation, (c) macrophage activation, endocytosis, and phagocytosis, and (d) CLC formation in phagosomes of activated macrophages. Peroxidase activity was present as follows: (a) in the matrix of eosinophil specific granules in eosinophil cytoplasm, in membrane-bound specific granules released into interstitial tissues from dying eosinophils, being phagocytized by activated macrophages, and within macrophage phagosomes; (b) as amorphous interstitial debris; (c) in cytoplasm and nuclei of damaged eosinophils in the dermal tissues as well as in macrophage phagosomes; and (d) in endocytotic vesicles and vacuoles of macrophages and in CLC-containing phagosomes of macrophages. CLC protein was localized by immunocytochemistry to (a) eosinophil primary granules, (b) cytoplasm and nuclei of damaged eosinophils located in the interstitial tissues or within macrophage phagosomes, (c) CLC located in interstitial tissues adjacent to necrotic eosinophils and in macrophage phagosomes, and (d) aggregates of amorphous protein bound to macrophage surfaces; endocytotic vesicles and vacuoles of macrophages; amorphous protein aggregates in macrophage lysosomes.(ABSTRACT TRUNCATED AT 400 WORDS)