Hematopoietic differentiative properties of murine spleen implanted in the omenta of irradiated and nonirradiated hosts.

Whole body irradiation of the recipients of syngeneic splenic implants into the omentum greatly enchances hematopoiesis and permits survial of and repopulation by stem cells of donor origin. Donor hematopioetic stem cells do not survive in spleen implants of the nonirradiated host; irradiated hosts were therfore used in the bulk of the experiments. Differentiation in the implants of splenic fragments is predominantly erythrocytic at 10 days and shifts to predominantly granulocytic differentiation at 21 days. Suspensions of spleen cells injected into the ometntum are predominantly granulocytopioetic at 10 days. The differntiation in fragments of spleen depleted of stem cells by irradtion, seeded with bone marrow cells and implanted into the omentum results in mixed erythocytic and granulocytic hematopoiesis, with granulocytic predominance. Lymphocytic cells appeared late in the implants of irrdiated recipients even at a time of prolific lymphocytopoiesis in the host's own spleens. The cause of the delay in the implants is not clear. The data are consisent with the concept that differntiation of hematopioetic stem cells is influenced by the stromal cells of the parent organ. The erythrocytic inductive capacity of the stromal cells may be lost by mechanical disruption or modified by irraidation or a prolonged period of implantation.