Leukocyte Labeling With ⁵¹Chromium. II. Leukocyte Kinetics in Chronic Myelocytic Leukemia

Sequential or simultaneous leukocyte kinetic studies using radioactive diisopropylfluorophosphate and radiochromate (⁵¹Cr) yielded similar or identical blood leukocyte disappearance curves in seven patients with chronic myelocytic leukemia (CML). Body surface ⁵¹Cr counting regularly showed a rise in the spleen counting rate during the first hours after infusions of granulocyte populations of mixed maturity. Epinephrine-induced leukocytosis was associated with a fall in the spleen counting rate, lesser decreases over the liver and marrow, rises in the heart and lung counting rates, and an unchanged blood leukocyte disappearance curve. These changes are consistent with the mobilization by epinephrine of a marginal granulocyte pool (MGP), which is largely localized in the spleen and is in equilibrium with the circulating pool. Immature CML granulocyte fractions were cleared from the blood more rapidly than mixed cell populations. The immature cells failed to equilibrate with the splenic MGP, and instead accumulated in the marrow and later recirculated into the blood as mature cells. These findings indicate that the delayed and variably contoured blood granulocyte disappearance curves found in CML are composites resulting from the recirculation of immature granulocytes in the presence of an enlarged total blood pool of mature cells.