Cellular responsiveness to stimulation in vitro: Strain differences in hemopoietic colony forming cell responsiveness to stimulating factor and suppression of responsiveness by glucocorticoids

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Abstract
Granulocyte‐macrophage colony formation from bone marrow cells in soft agar is dependent upon the presence of a stimulating factor and the number of colonies is related to its concentration. This dose‐response effect provided a measurement of the responsiveness to stimulation of colony forming cell populations in marrows from different sources. There were significant differences between the responsiveness of cells from different strains of mice which paralleled the previously observed myelopoietic and immune responsiveness of these strains to stimulation in vivo.Low concentrations of hydrocrotisone reduced the responsiveness of colony forming cells (a) when added to cultures of normal marrow or (b) when cells were taken from hydrocortisone‐treated mice and cultured in its absence. The reduction which followed inoculation was not apparent until the 4th day and occurred irrespective of mouse strain, type of drug or route of inoculation and with a dose (100 μg) which did not affect the actual number of colony forming cells in the marrow.