Genesis, ultrastructure and cytochemical study of the cat eosinophil

Eosinophils from cat bone marrow and peripheral blood were studied by electron microscopy and cytochemical procedures. The maturation of eosinophils and formation of typical granules were described. Contrary to the accepted opinion that the core of animal's eosinophilic specific granules have a crytal-like structure, our observations revealed that the core has a myelin-like cylindrical appearance, whose layered formation proceeds from the inside outwards. Electron microscopic observations revealed that localization of reaction product to potassium pyroantimonate and phosphotungstic acid and to acid phosphatase activity was similar to that of eosinophils of man and other animals. Antimonate deposits and acid phosphatase activity were detected between the layers of the myelin-like structure of the core. Eosinophil granules failed to yield a positive reaction for peroxidase activity. The secretory activity of the eosinophil is discussed.