Relative stability of inductive properties versus adaptable support capacity for hemopoietic colony formation in the spleen.

The capacity of stromal cells in heterotopic spleen implants to influence colony formation by injected CFU was studied after recovery of host mice from anemia, hypertransfusion or irradiation. The effect of irradiation on the prospective spleen implants was also studied. The ability of implanted spleens to attract CFU and support their colony formation was enhanced following post-implantation recovery in splenectomized, bled or irradiated hosts, whereas prior irradiation of the implant donors with 500 rad x-irradiation impaired these properties. Although slight changes were noted in the ratio of developing erythrocytic and granulocytic colonies, the characteristic inductive properties of the splenic HIM were not considerably changed following post-implantation recovery in non-perturbed or perturbed hosts. A period of anemia did not change the inductive properties and the extent of colony formation of in situ spleens, as measured after the mice had normalized their hematocrits. In contrast, in hypertransfused host mice, hyperplasia and increased colony formation was observed 2 weeks after mice regained their normal hematocrit values, but here also no shifts in E/G ratios were observed. The observations indicate that the characteristic inductive properties of the splenic stroma are quite stable. However, the capacity to attract injected CFU and initiate their colony formation can be manipulated to a great extent during a phase of splenic growth; also the induced changes remain established for a considerable period.