HEMATOPOIETIC CLONOGENIC CELLS (CFU-S) OF THE MOUSE EMBRYONIC LIVER UPON SHORT-TERM CULTIVATION IN-VIVO

The stem cell compartment of hemopoietic clonogenic cells (CFU-S) of m ouse embryos in a closed system was studied, when the hemopoietic tiss ue was devoid of supply of the hemopoietic cells and grafted into adul t recipients with diverse regulatory influences, The content of hemopo ietic clonogenic cells (CFU-S-7, CFU-S-11, and CFU-S-el) was determine d in the transplants of the 14-day embryonic liver placed under the re nal capsule of preirradiated syngeneic adult recipients. Relatively yo unger clonogenic cells (CFU-S-11) were practically absent from the tra nsplant in the end of cultivation, while the mote advanced stages (CFU -S-7) became more abundant, CFU-S-el were preserved in the transplant for 24 h, and they were absent by the fourth day of cultivation. Disap pearance of the clonogenic cells, which are referred to according to s ome properties as pre-CFU-S (CFU-S-el) from the stem compartment, a de creased content of another category of the clonogenic cells (CFU-S-11) , and an increased content of the more advanced cells (CFU-S-7) sugges t that in a closed system, maturation of the hemopoietic cells is acco mpanied by the exit of CFU-S to differentiation and is not compensated by their reproduction from the cells of earlier stages or self-reprod uction.