Erythropoiesis in lethally irradiated mice grafted with bone marrow or spleen cells

IN a recent paper OKunewick et al.1 reported that splenic erythropoiesis, denned as the 24 h uptake of iron-59 into the spleen, in mice lethally irradiated and grafted, depends on the source of the grafted cells. They found that grafting 106 bone marrow cells gave a greater uptake of iron-59 into the recipient spleen than grafting 106 spleen cells. In a second series of experiments, they found that 4 × 106 bone marrow cells grafted gave higher values than 4 × 107 spleen cells. They concluded that the relative erythropoietic activity of the spleen derived from spleen or bone marrow grafts is not a function of the number of cells administered and that the spleens are more erythro-poietically active if the animals have been grafted with bone marrow as opposed to spleen cells.