FACTOR(S) RESPONSIBLE FOR THE INCREASE IN ALKALINE-PHOSPHATASE ACTIVITY OF POST-MITOTIC GRANULOCYTES FROM NORMAL INDIVIDUALS AND PATIENTS WITH CHRONIC MYELOID-LEUKEMIA

Abstract

Using postmitotic granulocytes (PMG) with low neutrophil alkaline phosphatase activity (NAP activity), factor(s) having the capacity to increase their NAP activity were examined in vitro. A high activity of the factor was demonstrated in the cystic fluid of a human squamous cell carcinoma, which is known to produce a large amount of granulocyte-macrophage colony-stimulating factor (GM-CSF). The NAP-stimulating factor increased NAP values both in PMG from normal bone marrow and PMG from patients with chronic myeloid leukemia (CML); NAP values in cells treated with the factor approached or rose above those of normal peripheral granulocytes after 48 h of culture. The effect of the factor was specific in that the factor caused stimulation only in granulocytic series. Increases in NAP activity may reflect maturation of granulocytes; low NAP activity of neutrophils derived from patients with CML may be due to the immaturity of these cells. The relationship between the factor responsible for the increase in NAP activity and GM-CSF is also discussed.