The Effect of Continuous Cell Removal on Blast Cell Kinetics in Acute Leukaemia

Abstract

A 34‐year‐old male patient with acute myeloid leukaemia, who showed an exponential increase in blood leukocyte count during a second relapse despite intensive cytostatic therapy, was treated by leukopheresis using an IBM continuous blood cell separator. The rapid growth of cells was arrested and the patient thereafter responded to cytostatic therapy. Investigation of cell kinetics using 3H‐TdR in vivo just before the cen‐trifugation treatment showed that in spite of leukopheresis, which removed a total of 5 times 1012 cells, 3H‐TdR labelled leukaemic blast cells were observable in the peripheral blood as long as 42 d after injection, having presumably ‘become quiescent. An increase during leukopheresis in the mitotic index of blast cells in the bone marrow and in the labelling index of blast cells in the blood after in vitro incubation with 14C‐TdR led to the deduction that a feedback mechanism was acting within the leukaemic blast cell population.