Colony formation by chicken hematopoietic cells and virus‐induced myeloblasts

Leukemic myeloblasts and cells derived from normal chick hematopoietic tissue produced colonies in soft agar. Colonies produced by leukemic myeloblasts differed from normal chick tissue in their morphological characteristics, in the greater initial number of cells required for colony formation and in their decreased dependence on conditioned medium for development. The colony forming cells for both types were enriched when allowed to grow for several days in liquid growth medium. In soft agar, myeloblasts differentiated into more mature granulocytic cells and macrophages. These differentiated cells accumulated between one and two weeks after seeding. When tested for release of avian myeloblastosis virus (AMV), 6 out of 18 colonies were releasing AMV at one week whereas 3 out of 39 were releasing AMV at two weeks. Five two week old colonies which were negative for AMV were producing myeloblastosis associated viruses (MAVs). Normal colony forming cells were present in leukemic buffy coat and although colonies made by these cells contained MAVs, no AMV could be detected. The data obtained with normal avian tissues were similar to those obtained by others with mammalian hematopoietic tissue. Colony formation by normal hematopoietic tissues was strictly dependent on factors present in conditioned medium. Tissues producing colonies included bone marrow, yolk sac, spleen and peripheral leukocytes. Colonies were not obtained from thymus and bursa. Furthermore, the colony origin did not appear to be erythroid in nature.