ABSTRACT
The properties and functions of mouse pluripotential stem cells (CFU-S) were studied with spleen colony technique and other related methods. The data expressed that there is a linear relationship between the number of transplanted marrow cells and the number of spleen colonies that developed. Among various hematopoietic tissues, bone marrow is the richest source of CFU-S. Spleen and peripheral blood also contain a few of such cells. The percentages of CFU-S in these organs are 0.7%, 0.05% and 0.01% in sequence. No CFU-S can be found in thymus or lymph nodes. Under normal conditions, most of the CFU-S are in G_o phase with a small proportion (6.7%) in S phase.Self-renewing capacity, an important hematopoietic function of CFU-S, was measured by the experiments of single spleen colony retransplantation. The value of the probability of self-renewal, p, is calculated as 0.76. CFU-S has an active ability of migration. It was found that a number of CFU-S either from the marrow cell suspension injected intraperitoneally or from an entire encapsulated spleen which was placed free in the peritoneal cavity after ligation of its blood vessels can penetrate through a lot of barriers to develop spleen colonies in the lethally irradiated mice. A dose of 500～700 rad ?-irradiation apparently stimulates the CFU-S migrating from bone marrow to circulation.