Peripheral Cytoplasmic Characteristics of Leukocytes in Monocytic Leukemia: Relationship To Clinical Manifestations

The increased prevalence of tissue infiltration in some cases of monocytic leukemia may represent an enhanced ability of monocytes for tissue entry, continued cell proliferation, an increased life span in the tissues, or a combination of these three factors. Studies in this laboratory have shown that the normal myeloblast undergoes a process of cytoplasmic maturation that adapts it for marrow egress, tissue emigration, and particle ingestion. These include a reduction in surface negative charge density, increased ability to adhere to negatively charged surfaces, increased cytoplasmic deformability, more rapid motility, and enhanced phagocytic rate. In a subject with monocytic leukemia in whom tissue infiltration was a striking feature of the clinical disease, blood monocytes were broadly distributed in regard to their peripheral cytoplasmic characteristics. One portion of the cell population had a high surface negative charge density, was weakly adherent, weakly phagocytic, and poorly deformable, akin to blast cells. A second portion of the cell population had lower surface negative charge density, was adhesive, phagocytic, and readily deformable, akin to mature blood phagocytes. In five patients with myeloblastic leukemia in whom tissue infiltration was not prominent and in whom 92% of cells were myeloblasts, the blood leukocytes had a more homogeneous distribution of surface properties, and these properties were characteristic of immaturity. The increased prevalence of tissue infiltration in some cases of monocytic leukemia may be due to the presence of cytoplasmic maturation, which normally adapts the monocyte for tissue entry.