Characteristics of Cell Proliferation in Children's Lymphoblastic Leukemia

Abstract

The proliferative activity of the bone marrow and peripheral cells of acute infant lymphoblastic leukemia was evaluated by « in vitro » incorporation of thymidine-H₃. The proliferative activity of leukemic lymphoblasts proved roughly similar to that already observed in hemocito-myeloblastic acute leukemias of adults. Within the lymphoblastic population, incorporation of tritiated thymidine was distributed very heterogeneously and there was no labelling of the smaller blasts. In the larger blasts, the labelling index increased progressively with the increase in cell diameter. The acute leukemia population can thus be divided into two classes: proliferating and non-proliferating. A study of the proliferative activity of lymphoblasts, contemporaneously in bone marrow and peripheral cells, suggested a division of cases into two groups. In one proliferative activity in the marrow was greater than in the peripheral blood; in the other it was equal to or less than in the peripheral blood. The second group was made up of cases whose clinical features presented a much more marked hepato-splenomegaly and high peripheral leucocytosis. A more detailed study of proliferative activity considering various classes of blasts within the same population showed that, in the first group of patients, the highest percentage of large blast cells is found at bone marrow level, while in the second the percentage of large blasts in the marrow is equal to or less than that observed in the peripheral blood. It was also shown that total proliferative activity is correlated to the percentage of large blasts. On the basis of these findings, one may admit that in first group forms the leukemia cells are generated prevalently in the bone marrow, while in second group forms most leukemic cells are formed elsewhere.