A COMPARATIVE STUDY OF THE REPOPULATING POTENTIAL OF GRAFTS FROM VARIOUS HAEMOPOIETIC SOURCES: CFU REPOPULATION

The growth rate of the CFU populations in spleens and femora has been studied in irradiated mice injected with cell suspensions, containing equivalent number of CFU, from various sources. The doubling times are shown to be dependent upon the source of the cells. Grafts of bone marrow, spleen and foetal liver cells produced doubling times in the spleen of approximately 25, 19 and 16 hr respectively. Grafts of marrow-derived and spleen-derived spleen colony cells both gave rise to CFU doubling times lower than those of the corresponding primary grafts (approx. 33 and 26 hr respectively in the spleen). In the case of both bone marrow and spleen grafts the CFU population growth was shown to be independent of the size of the graft. A hypothesis is advanced which invokes at least a dual population of CFU, having different doubling times, different seeding capacities in the haemopoietic tissues following i.v. injection and present in different proportions in the various haemopoietic tissues.