Proliferation inhibition of murine pluripotent haemopoietic stem cells by interferon or poly I:C

The effect of mouse serum interferon (IF) in vitro and an inducer in vivo on the proliferation of a pluripotent stem cell population with high turnover rate was studied. Proliferation rate was characterized by the number of CFUs in the S phase of the cell cycle. Increased proliferation of bone marrow stem cell populations was produced either by irradiating the donor mice with 3.36 Gy (336 rad) 60Co-gamma rays 7 days before the experiment or by incubating normal bone marrow cells with 10(-11) M concentration of isoproterenol. IF considerably reduced the number of CFUs in S phase in both cases without reducing the CFUs content of the samples. Injection of IF inducer (4 mg/kg poly I:C) into regenerating mice also inhibited the proliferation of CFUs without decreasing the femoral CFUs level. Regeneration kinetics of CFUs from irradiated poly I:C-treated mice ran parallel with that of irradiated untreated animals but showed a characteristic delay corresponding to approximately one CFUs doubling. A transient, non-cytotoxic proliferation inhibitory effect of IF or IF inducer is, therefore, proposed.