In vitro colony-forming cells in embryonic mouse liver, spleen and peripheral blood.

The number of in vitro colony-forming cells (CFC) was examined in embryonic livers, spleens, and peripheral blood of C57B1/6J mice from the 12th to the 19th day of gestation. Peaks of CFC in the liver and spleen were noted on days 13, and 15, respectively, whereas the number of CFC in the peripheral blood remained almost constant. The possibility that CFC in the embryonic mouse are produced both in the yolk sac and in other hemopoietic sites is discussed.