Differences in the Proliferative Activity of Myelocytes from Bone Marrow, Spleen and Peripheral Blood in Chronic Myeloid Leukaemia

Cells from bone marrow, spleen and peripheral blood from 8 patients with chronic myeloid leukaemia were incubated with tritiated thymidine under standardized conditions. The labelling of myelocytes was determined by autoradiography after incubation for 10, 20 and 40 minutes. Maximal labelling was observed after 40 minutes of incubation with an equal proportion of myelocytes labelled in bone marrow, spleen and peripheral blood. However, the rate of thymidine incorporation in spleen myelocytes increased with increasing signs of relapse. There was no such increase in the rate of incorporation in the bone marrow and peripheral blood myelocytes. On the contrary, in the bone marrow the lowest rate of thymidine incorporation was seen in relapse. In one patient examined before and during treatment with busulphan, treatment caused a reduction of the rate of thymidine uptake into the spleen myelocytes. There was no effect on the incorporation of thymidine into bone marrow or blood myelocytes. One patient examined just prior to a blastic crisis was found to have a strongly reduced rate of thymidine uptake into the spleen myelocytes. The results indicate differences in the proliferative activity of granulopoietic tissue in bone marrow and spleen. The differences become more pronounced with increasing leucocyte counts.