Kinetic models of hemopoietic stem cell populations

Summary Recent techniques enabled a series of quantitative studies to be made with various aspects of the stem cell functions. Results from several laboratories appear to agree on certain main points: the existence of a pluripotential stem cell in the small rodent, capable of forming visible colonies of hemopoietic foci in the spleen and the existence of some undifferentiated but committed precursor cells from which the differentiating and maturing cell populations originate. There is evidence that the primary stem cell is in a low turnover state in the normal animal, although on demand it is capable of fast and prolonged proliferative activity. The committed undifferentiated precursor cells differ greatly, depending on which cell line they represent. Some of these are in high turnover state in the normal animal (e.g., erythropoietin-responsive cells), others do not appear to be capable of proliferation (e.g., focus forming cells). Perturbation of the steady states by irradiation of the animal, or by treatment with cytotoxic drugs results in recovery patterns which yield valuable kinetic information.