Use of spleen organ cultures in the analysis of hemopoietic alterations induced by irradiation and allogeneic marrow transplantation.

The transplantation of 0.5-1 X 10(7) BALB/c mouse bone marrow cells into lethally irradiated CBA recipient mice and the subsequent explantation of the recipient spleens resulted in active hemopoietic progenitor cell (colony forming cell; CFC) regeneration in organ cultures but not in vivo. In order to establish what hemopoietic elements essential for CFC regeneration are altered in vivo as a consequence of allogeneic donor/recipient interactions, the ability of spleens to support CFC regeneration in organ cultures was analysed when these were removed from irradiated recipients at various time intervals after allogeneic marrow transplantation. It was found that an inhibition of differentiation of hemopoietic stem cells (CFUs) and committed hemopoietic progenitor cells (CFC) occurred initially in allogeneic marrow graft recipients followed by an alteration of growth supportive spleen stromal elements. The latter appears to consist of at least two distinct components: a nonspecific component and a specific component with the features of immunologic memory.