Erythrocyte Fe59 uptake as a function of bone marrow dose injected in lethally irradiated mice.

I T IS well-established that repopulation of hemopoietic tissue occurs in lethally irradiated mice given bone marrow.1 The relation of survival2 and spleen recolonization3 to bone marrow close has been described, as has that of spleen cell dose to antibody production4 in lethally irradiated mice. It is probable that the cell responsible for repopulation of erythropoietic tissue is the stem cell and not a cell from what has been called the “bone marrow proper” compartment, for cells in the latter compartment are considered not to be self-maintaining.5 The fact that bone marrow from plethoric animals, whose marrow is devoid of recognizable erythropoietic elements, can repopulate erythroid tissue of lethally irradiated mice#{176}’7argues in favor of this view. Thus, it would be of interest to establish the relation between dose of bone marrow and magnitude of erythropoiesis in a lethally irradiated recipient. This relation would give an indirect measure of the number of stem cells in marrow, and could be used to determine factors influencing the stem cell pool size. The lethally irradiated mice used as recipients can be thought of as an “in vivo culture medium” for these cells.3’8 The purpose of this communication is to describe the relation between isologous, homologous, and heterologous bone marrow dose and the magnitude of erythropoiesis as measured by uptake of Fe 9 in erythrocytes9’1#{176} in lethally irradiated mice. The effects of erythropoiesis stimulating factor (ESF) and of preimmunization with homologous and heterologous marrow on erythrocyte F&11 uptake are also described.