Effects of Radiation on The Capacity of The Stem Cell Compartment to Differentiate into Granulocytic and Erythrocytic Progeny

A VARIETY OF METHODS have been used to investigate the properties of the stem cell#{176} compartment.’#{176} The spleen colony method introduced by Till and McCullocW measures the production of hematopoietic colonies after injection of syngeneic bone marrow into irradiated recipient mice. These colonies appear to be the progeny of single cells’0 which are able to differentiate to form either granulocytic or erythrocytic progeny.� Under most circumstances, the system is more a measure of erythrocyte production since the surface colonies in the spleen are predominantly concerned with erythropoiesis.12’5 Other technics which measure proliferation of hematopoietic cells within the spleens of animals recovering from whole body irradiation utilize spleen weight,2 incorporation of IUDR into the DNA of newly-formed cells,’ or incorporation of 59Fe into maturing erythrocytic cells.4 A second type of assay system ( repopulating ability ) measures the ability of transplanted progenitor cells to form specific mature progeny. Irradiated recipient animals having received syngeneic bone marrow earlier will incorporate 59Fe into newly-formed erythrocytes. If one waits a sufficient period of time for proliferation and differentiation of the injected bone marrow progenitor cells before injecting the radioactive iron, then the incorporation of 59Fe is proportional to the number of bone marrow cells injected, and canbe used to assay such marrow.5 Hodgson compared irradiated with normal marrow and constructed a radiation survival curve.6 Using this as a model, we have described a similar system in which the granulocytic progeny of the injected marrow are measured.#{176} In this system, irradiated recipient mice are given syngeneic bone marrow, a period of time is allowed for this marrow to proliferate and differentiate, and then bacterial endotoxin is injected. The peripheral white blood cell response to bacterial endotoxin has