Fig. 1.

Terminal erythropoiesis stimulated in Lin⁻ BM cells over 3 days in culture. BM cells were stained with biotinylated α-Lin mAbs, and the Lin⁺ fraction of the population was subsequently removed to obtain a progenitor-rich population (Lin⁻ BM). These Lin⁻ cells were then cultured in vitro for 3 days on fibronectin-coated plates in medium containing serum. Epo was included in the medium for the first day of culture, and then the medium was changed, and Epo was removed. The differentiation profile of the cultured cells was examined by both flow cytometry and benzidine–Giemsa stain after each day in culture, and a representative micrograph of these stained populations is presented from each day of erythropoieitc culture. After the third day of culture, flow cytometry indicated that the majority of the resulting population had acquired a late erythroid surface phenotype (Ter-119⁺). Furthermore, benizidine–Giemsa staining revealed that many cells in the harvested population had enucleated and expressed hemoglobin. The arrowhead indicates a hemoglobin⁺ normoblast, and the arrow indicates an enucleated reticulocyte. (Scale bars, 20 μm.)