Transplantation of Various Numbers of Foreign Bone-marrow Cells in Mice after Lethal and Supralethal X-irradiation

Abstract
Survival of irradiated mice treated with sub-optimal numbers of allogeneic bone-marrow cells could not be improved by addition of a large number of bone-marrow cells derived from the same donor strain and made incapable of proliferation by irradiation with 3000 r. This argues against the absorption of "natural antibodies" by excess of antigen. Survival-curves of mice treated with sub-optimal numbers of allogeneic bone-marrow cells showed the greatest mortality in the period of 10-20 days after lethal irradiation. This mortality was diminished if the hosts were irradiated with supralethal X-ray doses. In the combinations studied the number of required allogeneic or rat marrow cells was decreased after supra-lethal irradiation of the recipients. Determinations of the number of nucleated cells present in bone-marrow and spleen showed a continuous increase in lethally-irradiated mice treated with syngeneic cells and in supralethally-irradiated mice treated with allogeneic cells. In lethally-irradiated mice treated with allogeneic bone-marrow cells, this increase was interrupted at about 14 days after irradiation by a small transitory remission. These data were explained on the basis of an active immunological response after an extended induction period in lethally-irradiated mice treated with foreign cells. After supralethal irradiation this residual response is depressed. Stimulation of the phagocytic activity of the RES through zymosan injections did not decrease survival of lethally- and supralethally-irradiated mice that were treated with allogeneic or rat bone-marrow suspensions. Instead there was a tendency toward a beneficial effect on survival.