Ultrastructure of simian eosinophils.

The ultrastructure of eosinophil granulocytes has been studied in the bone marrow and nasal mucosa of the monkey. Both the mature eosinophils and their precursors, including the form and dimensions of their granules, were generally similar to those of man and rodents. Unusual features in the marrow were the occasional presence of an irregular substructure in granules without interna, or of cytoplasmic vacuoles containing material apparently derived from granule breakdown. In the nasal mucosa, eosinophils were present in both the epithelium and in the sub-epithelial tissues. The lattice arrangement of the eosinophil internum had a spacing of up to 5-4 nm, with sometimes a secondary repeat of 2-7 nm, and suggested a more complex crystal structure than that of man and rodents.