The relative effect of h-2 disparity between irradiated host and injected bone marrow cells on their total proliferative and erythropoietic activities in the host's spleen.

Previous experiments showed that in the spleen of non-syngeneic (H-2 disparate) irradiated hosts, the colony-forming performance of injected bone marrow cells may be markedly lower than the standard syngeneic performance. There were also some indications that the deficit was due to a deviated differentiation of the pluripotent stem cells into an alternative pathway. In the present study, the total proliferative activity of donor bone marrow cells [B10.A(2R)] in the syngeneic or allogeneic [B10.A(5R)] hosts was measured as the rate of uptake of 125IUdR and the erythropoietic activity as the rate of uptake of 59Fe. Since both activities are linear functions of the number of injected cells, their inhibition in allogeneic hosts could be judged by the relative slopes of the comparable regression lines. Well reproducible results showed that the erythropoietic activity was inhibited more than the total proliferative activity; this suggests that the residual component of the total proliferative activity must be inhibited less (or even stimulated) in the allogeneic host. The possibility that the differential effect of the allogeneic host environment on the total and erythropoietic activities might be due to a deviated differentiation of some pluripotent cells into the lymphopoietic pathway is discussed.