[Effect of the stem cell inhibitory factor on the formation of hemopoietic colonies]

The activated T lymphocytes release in the culture medium a factor inhibiting the ability of hemopoietic stem cells to form hemopoietic colonies in the spleens of lethally irradiated recipients. An analysis of the effect of this factor on hemopoietic colonies was carried out. Its inhibiting effect was not related to the process of opsonization and to changes in the migration of spleen cells in the irradiated organism. No marked changes in the ratio of erythroid, myeloid and megakaryocytic foci were found in the spleens of irradiated mice which received the syngeneic bone marrow cells treated in vitro by the factor of stem cell inhibition: all three sources of hemopoiesis suffered under its effect to the same extent and their total number of the spleens was sharply reduced. Some mechanisms of the effect of the factor of stem cell inhibition on the formation of hemopoietic foci are discussed.