Colony forming units and haematopoietic stem cells in osteoclastopoiesis.

HSC and CFUs are not identical. HSC are no longer considered to be a homogeneous population but an age-structured spectrum of cells (Schofield, 1978). CFUs, which have been identified only in rodents and with certainty only in mice, may be a sub-set of HSC required by mice, perhaps controlled by the W locus and virtually eliminated in double W mutants. A dichotomy of CFUs and HSC has also been demonstrated by Wiktor-Jedrzejczak et al. (1977); ++ bone marrow treated with anti-Thy 1.2 serum lost its curative properties for W Wv anaemic mice with CFUs being unaffected.