Characteristics and functions of monocytes and promonocytes in monocytic leukemia

The characteristics of mononuclear phagocytes (promonocytes and bone-marrow and blood monocytes) of 27 patients with acute or chronic monocytic leukemia were studied. The percentages of promonocytes with peroxidase and esterase activity and of cells with Fcgamma and C3b receptors showed some divergence from those found in normal individuals. The phagocytic activity of monocytes and their ability to kill ingested Staphylococcus aureus were not decreased in this group of patients. The 3H-thymidine-labeling index of the promonocytes did not differ greatly from normal values, which indicates that the percentage of dividing promonocytes had not increased. The very low labeling index of the circulating monocytes means that these cells do not divide and therefore cannot be blast cells or monoblasts.