Hemopoietic colony-forming cell responses in mice infected with ectromelia virus

The responses of in vitro colony-forming cells (granulocyte-macrophage progenitor cells) were studied in the bone marrow, spleen, and blood of mice after intraperitoneal injection of 10(3) plaque-forming units of ectromelia virus. This study showed that a colony-forming cell response occurred during infection and was accompanied by an increase in the serum level of colony-stimulating factor and, at a later stage, colony-inhibiting factor. Changes in the proportions of colony-forming cells were not due to relative changes in other cell populations. The relationships between colony-forming cell responses and levels of infection were complex, higher levels of infection being associated with good colony-forming cell responses in bone marrow and apparently poor colony-forming cell responses in blood and spleen.