The effect of cyclic AMP on human colony forming cell and colony stimulating factor production

The use of peripheral blood feeder layers as a source of GM-CSF for human bone marrow cultures

The use of peripheral blood feeder layers as a source of stimulus for colony formation by human granulocytic progenitor cells in semi-solid agar cell cultures was examined. Comparison with various conditioned media demonstrated that cultures stimulated by peripheral blood feeder layers produced the greatest number and largest colonies. The cell concentration in the feeder layers was more important than the total cell number. Feeder layer plates containing 2 X 10(5) cells at a concentration of 1 X 10(6) cells/ml proved to be just potent as the conventional feeder layer plates containing 1 x 10(6) cells/ml in 1 ml. Thus feeder layer plates can be more economical in terms of cell numbers than has previously been reported. By using a known panel of donors for the leukocytes, the number of sub-optimal batches of feeder layers was reduced. Addition of 1 microM adenosine 3':5'-cyclic-monophosphate or 10 micrograms/ml Li2CO3 to poor feeder layers enhanced their colony-stimulating ability.

Regulation of hemopoietic cell differentiation and proliferation

Differentiation and proliferation of almost all hemopoietic cell lines can now be studied in vitro. Cloning techniques and suspension cultures allow the study of proliferation of the multipotential hemopoietic progenitor cell and the committed progenitors for granulocytes, macrophages, eosinophils, megakaryocytes, and erythrocytes. The proliferation of each of the committed progenitor cells is controlled by specific glycoproteins and two of these have recently been purified: granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin. The rate of proliferation of the GM-progenitor cells and their pattern of differentiation depends on the concentration of the hormone. At low concentrations of GM-CSF (10(-11) M) fewer progenitor cells are stimulated and macrophage colonies rather than granulocyte colonies develop. The change in the direction of granulocyte-macrophage differentiation appears to be related to a) the concentration of GM- CSF and b) the different sensitivity of a subpopulation of monocyte colony-forming cells which are responsive to GM-CSF even at low concentrations of the regulator. Analysis of the rate of RNA synthesis by bone marrow cells has shown that GM-CSF stimulates the mature nondividing end cells of differentiation (ie, polymorphs) as well as the progenitor cells. Although GM-CSF and erythropoietin have been radiolabeled, binding studies have been hampered by the loss of biologic activity during the labeling procedure and the heterogeneity of the target cells to which the regulators bind. Surface proteins and receptors for erythrocytes have been well characterized but the relationships between these proteins and the cell surface proteins of nucleated blood cells is not well understood. It appears that some proteins are lost from the cell surface during the development of granulocytes, which are retained on the surface of the B lymphocyte. Other proteins such as chemotactic receptors and complement receptors only appear on the mature cells. External radiolabeling of the granulocyte surface using iodogen yielded a simple profile of 125I-labeled proteins when analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis.