Cytochemical and Morphologic Identification of Macrophages and Eosinophils in Tissue Cultures of Normal Human Bone Marrow

When normal human bone marrow cells are cultured in soft agar, in the presence of human spleen-conditioned medium, two types of colonies could be recognized by means of the inverted microscope: large colonies consisting of macrophages— monocytes, and small colonies consisting of eosinophils. In the two types of colonies, cells developing from blasts to mature cells could be recognized by their morphologic and cytochemical properties. The identification of macrophage-monocytes and of eosinophils was based on light, phase-contrast, and electron microscopy, the strong positive reaction of α-naphthyl acetate esterase in the macrophage-monocyte, and the positive stain with Luxol Fast Blue, eosin, and peroxidase of the eosinophils.