| Abstract: | Properties of the cells (TE-CFU) that give rise within four to six days to transient endogenous erythropoietic spleen colonies in irradiated mice have been investigated. The results obtained indicate that (1) erythropoietic maturation within such colonies is highly erythropoietin-dependent, (2) the population size of TE-CFU is not erythropoietin-dependent, (3) initial exposure to a high dose of erythropoietin followed by continuing exposure to lower doses is required for maximal efficiency of colony formation by TE-CFU, (4) successful transplantation of TE-CFU has not been achieved, but they appear among the progeny of transplanted hemopoietic cells, (5) TE-CFU are defective in mice of genotype W/Wv. These findings are consistent with the view that the TE-CFU assay detects a class of early erythropoietin-sensitive progenitor cells committed to erythropoietic diffferentiation, rather than "abortive" colony formation by pluripotent stem cells. |
