Myelopoiesis controlling agents in vitro

Abstract

The effect of sera from leukopenic and leukocytotic rabbits on normal rabbit bone marrow was studied in vitro. The rate of formate-C14 incorporation served for measuring the mitotic rate. Sera collected in the leukopenic phase or in the initial phase of leukocytosis, and incubated with normal bone marrow, were found to increase formate-C14 incorporation into cells significantly. On the other hand, sera collected at the peak of leukocytosis inhibited formate incorporation. Bone marrow from control rabbits incubated with sera from leukopenic and leukocytotic animals produced a characteristic change in the mitotic rate and in the ratio of myeloid precursors and mature myeloid elements. Kinetics of formate incorporation qualitatively agreed when bone marrow from leukopenic, leukocytotic, and control rabbits was incubated with the animals' own sera, or when bone marrow from control rabbits was incubated with leukopenic and leukocytotic sera, respectively. It may be assumed that the agents considered represent the humoral system maintaining the homeostasis of myeloid elements.