Proliferation and differentiation of highly enriched mouse hematopoietic stem cells and progenitor cells in response to defined growth factors.

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Abstract
Three distinct hematopoietic populations derived from normal bone marrow were analyzed for their response to define growth factors. The Thy-1loT-B-G-M- population, composing 0.2% of bone marrow, is 370-fold enriched for pluripotent hemopoietic stem cells. The two other populations, the Thy-1-T-B-G-M- and the predominantly mature Thy-1+T+B+G+M+ cells, lack stem cells. Thy-1loT-B-G-M- cells respond with a frequency of one in seven cells to IL-3 in an in vitro CFU-C assay, and give rise to many mixed colonies as expected from an early multipotent or pluripotent progenitor. The Thy-1-T-B-G-M- population also contains progenitor cells which responded to IL-3. However, colonies derived from Thy-1-T-B-G-M- cells are almost exclusively restricted to the macrophage/granulocyte lineages. This indicates that IL-3 can stimulate at least two distinct clonogenic early progenitor cells in normal bone marrow: multipotent Thy-1loT-B-G-M- cells and restricted Thy-1-T-B-G-M- cells. Thy-1loT-B-G-M- cells could not be stimulated by macrophage colony-stimulating factor (M-CSF), granulocyte CSF (G-CSF) or IL-5 (Eosinophil-CSF). The hematopoietic precursors that react to these factors are enriched in the Thy-1-T-G-B-M- population. Thus, multipotent and restricted progenitors can be separated on the basis of the expression of teh cell surface antigen Thy-1.