Electron Microscopic Study of Human Basophils

Electron microscope studies were carried out on human basophils obtained from peripheral blood and thoracic duct lymph. Delineation of the cells in thick sections was facilitated by staining with Toluidine Blue, which imparted the characteristic purple-red color to the granules. The cytoplasm contains many of the organelles seen in other cells, including a small Golgi apparatus, centrioles, mitochondria, fibrils and microtubules. Ribosomes and rough ER are rarely encountered. Basophil granules are surrounded by a unit membrane and contain particles which are uniform in size within the same granule but which vary in size in different granules within the same cell. Some granules reveal a homogeneous texture and/or "myelin" figures. The appearance of most basophil granules differs from the ultrastructure of human mast cell granules reported to date. It is suggested that the difference in fine structure may reflect a difference in the chemical constituents of the granules.