Quantitative measurements on the haemopoietic systems of three strains of mice.

Quantitative measurements on the haemopoiedic systems of SAS/4, 3H and RFM mice have been used to calculate the distribution and population sizes of haemopoietic cells in the bone marrow, spleen and peripheral blood. Considerable strain differences have been found in the sizes of haemopioetic stem cell populations and in the distribution of these cells within the haemopioetic system, although the incidence of CFU-S was shown to be uniform throughout skeletal sites of haemopioesis. The seeding efficiency of colony forming cells in the spleen, measured by the 'f" factor 24 hours after irradiation and transplantation, also differs between strains and between the bone marrow and spleen of the strains investigated.