Abstract
High enriched populations of hematopoietic progenitor cells were obtained by isolating lineage negative (Lin super(-)), Thy-1-positive (Thy-1 super(+)) fresh bone marrow cells, or by isolating cells from interleukin-3 (IL-3) supplemented bone marrow cultures expressing Thy-1 antigen with the fluorescent activated cell sorter. TGF- beta 1 inhibited IL-3-induced Thy-1 expression on Thy-1-negative (Thy-1 super(-)) bone marrow cells in a dose-dependent manner. In addition, TGF- beta 1 inhibited the formation of multipotent and mixed colonies by isolated Thy-1 super(+) cells, while single lineage granulocyte and macrophage colonies were not affected. The growth of Thy-1 super(+) Lin super(-) cells incubated as single cells in Terasaki plates in medium supplemented with IL-3 were inhibited by TGF- beta , demonstrating a direct inhibitory effect. TGF- beta 1 inhibited the growth of all subpopulations of high proliferative potential (HPP) colony forming cells (CFC) in a dose-dependent manner. Thus, TGF- beta directly inhibits the growth of the most immature hematopoietic cells measurable in vitro.