In vitro studies, utilizing an organ culture method were reported on mutual interactions between irradiated spleen, normal bone marrow, and thymus. It has been shown; (a) that singly isolated spleen explants were incapable of lymphoid regeneration, (b) thymus had no stimulatory effect on spleen regeneration, (c) bone marrow interacted synergistically with spleen leading to appearance of lymphoid cells which were not detected in singly isolated bone marrow or spleen, and (d) no stimulation of lymphopoiesis in bone marrow was conferred by thymus in the absence of spleen.
The results are discussed in terms of possible mechanisms involved in lymphoid radiation recovery in vivo.