Our data does not describe the relationship between these two populations: we do not know if the leukemia cells are monoclonal, and hence arising from a subsequent mutation in a progenitor cell that is already predisposed to have inhibited terminal differentiation; or whether these cells are polyclonal arising in a separate population that is negative for GR-1, CD-11b or B220 that has a competitive advantage. The gene discussed is PTPRC; the disease is leukemia.