In vitro thymidine uptake by circulating leukocytes.

Abstract

Abstract Determination of isotope uptake by leukocytes in diluted whole blood incubated with 3 H-thymidine proved to be a very sensitive method for detecting DNA-synthesizing cells in the circulation. Among normal subjects, uptake per unit volume of blood did not correlate with either lymphocyte or granulocyte counts, and probably reflected a low level of "spontaneous blastogenesis" among circulating lymphocytes. Thymidine uptake was normal or modestly elevated in a number of nonleukemic disease states. In chronic lymphocytic leukemia, uptake values ranged from subnormal to grossly elevated levels, were relatively stable, and correlated with aggressiveness of the disease. Low or normal values uniformly predicted a favorable near-term course. In chronic myelocytic leukemia, thymidine uptake appeared to be principally into immature granulocytes, correlated with white blood cell count and percentage of immature cells, was acutely affected by treatment, and could fluctuate rapidly and widely. Among patients in stable "good" control of the disease, uptake values correlated with course during the subsequent year. Measurement of in vitro leukocyte thymidine uptake can identify the presence of proliferating cells in the circulation, not detectable by routine hematologic studies. It should prove particularly useful in monitoring the status of patients with leukemia and related disorders.