Effects of allogeneic stimulations on the proliferation and differentiation of the hemopoietic stem cell.

The effects of allogeneic stimulatins on the hemopoietic system were investigated. Spleen cells of mice activated in vivo with alloantigens were able to produce highly active colony-stimulating factor in the culture medium without any stimulation. But spleen cells of these mice could not release colony-stimulating factor after treatment in vitro with anti-theta serum and complement. The number of granulopoietic progenitor cells (colony-forming unit-culture) in both bone marrow and spleen cells of mice treated with such procedures was significantly greater than that of the control, and the number of pluripotent stem cells (colony-forming unit-spleen) of these mice was markedly increased compared with that of the control, especially in spleen cells. These experiments suggest that T lymphocytes activated in vivo with alloantigens may release active substances in the differentiation and proliferation of hemopoietic stem cells.