Haemopoietic stem cells in leukaemic AKR mice: the (AKR x C57BL/6)F1 mouse as an in vivo assay system.

Characteristics of the AKB6F1 mouse strain make it suitable as an assay animal for quantitating haemopoietic stem cells, or spleen colony-forming units (CFU-S), from leukaemic AKR mice. Marrow cells harvested from leukaemic mice were assayed for CFU-S in lethally irradiated AKR or AKB6F1 hosts. Survival times and numbers of leukaemic colony-forming units (L-CFU) in unirradiated recipients were used to detect proliferation of transplanted leukaemic cells. In contrast to AKR recipients, the proliferation of transplanted leukaemic cells was suppressed in F1 hosts. Injection of marrow cells from normal nonleukaemic AKR mice into AKR and F1 hosts yielded significantly more CFU-S and spleen 59Fe uptake in F1 than in AKR hosts. In marked contrast, injection of marrow from leukaemic AKR mice suppressed CFU-S proliferation in the F1 recipients. Thus it was possible to quantitate CFU-S in marrow containing L-CFU.