An antigenic difference between cells forming early and late haematopoietic 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)¹. However, recent evidence suggests that there are distinct sub-populations of CFU-S². 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 days². Furthermore, many 10-day-old spleen colonies do not contain cells capable of forming spleen colonies in secondary irradiated recipients (an index of the self-renewal capacity of stem cells) whereas at day 14 almost all colonies contain these CFU-S³. These studies suggest that only when colonies are scored at or later than 11–12 days is the spleen colony technique adequate for the assay of multipotential stem cells. We now report an antigenic difference between subpopulations of CFU-S forming early (day 8) and late (day 14) spleen colonies which has been used to purify multipotential haematopoietic stem cells from murine bone marrow.