Purification of rat pluripotent hemopoietic stem cells

A method for isolating rat hemopoietic stem cells (HSC) using albumin density gradient fractionation of cortisone-treated rat marrow followed by staining with anti-Thy-1 antibody and sorting on a fluorescence-activated cell sorter is described. The HSC fraction obtained in this way contains 100% pluripotent stem cells as judged by spleen colony formation assays and by the capacity of these fractions to protect lethally irradiated rats. The inclusion of the density separation step allows significant reduction in sorting time, if more than 2 X 10(5) HSC have to be isolated. The yield of this procedure is 40-45% of the initial number of HSC in cortisone-treated rats.