AN ANTIGENIC DIFFERENCE BETWEEN CELLS FORMING EARLY AND LATE HEMATOPOIETIC SPLEEN COLONIES (CFU-S)

Abstract

Murine pluripotent haematopoietic stem cells have generally been assayed by their ability to form macroscopic colonies of haematopoietic cells in the spleens of heavily irradiated recipient mice (colony-forming unit-spleen or CFU-S assay). However, recent evidence suggests that there are distinct subpopulations of CFU-S. Most spleen colonies present 7-8 days after injection consist of differentiated erythroid cells, contain no primitive myeloid or erythroid precursor cells and disappear from the spleen within 3 days, whereas the majority of colonies present at 10-12 days contain primitive precursors, are multilineal and cannot be detected at 7-8 days. Furthermore, many 10-day-old spleen colo..