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STRUCTURE OF EOSINOPHILS

Human eosinophils, unlike neutrophils, usually have a bilobed nucleus (Fig. 23.2). Defining attributes of eosinophils are their large, cytoplasmic ‘specific’ granules that are morphologically distinct because of their unique content of crystalloid cores. Crystalloid cores are recognizable by transmission electron microscopy and usually appear electron dense (Fig. 23.2). The cores and surrounding matrices of specific granules contain cationic proteins that account for the tinctorial staining of granules with eosin. Eosinophils at sites of inflammation can exhibit morphologic changes in their specific granules, including loss of either matrix or core components from within intact granules, compatible with the extracellular release of granule constituents.

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Lipid bodies, cytoplasmic structures distinct from granules (Fig. 23.2), are roughly globular in shape and range in size from minute to the size of specific granules. Lipid bodies are dissolved by common …