Action of Humoral Factors Derived from Acute and Chronic Myeloid Leukemic Cells on In Vitro Myelopoiesis

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Abstract
The experiments described in this paper were performed to elucidate a possible regulatory role of acute and chronic myeloid leukemic leukocytes. The influence of these cells on activated or nonactivated mouse bone marrow cells was measured, and the results were compared with the action of the 2 major leukocyte fractions, mononuclear cells and granulocytes. Acute leukemic blasts were almost completely unable to activate myeloid committed stem cells (colony forming units, CFUC). Blasts from patients with chronic myeloid leukemia (CML) in blastic crisis disclosed a variable pattern of activation, in that 2 of 3 cases exerted normal stimulatory capacity. A possible inhibitory action of leukemic cells was the subject of further experiments. Acute leukemic blasts in some cases disclosed inhibitory activity, a few cases appeared to be without influence on normal proliferating CFUC. Granulocytes from patients with CML in the chronic phase showed inhibitory capacity when compared with granulocytes from normal individuals. Leukemic cells themselves may contribute to the regulatory derangements of leukemias.