Control mechanisms of endotoxin and particulate material stimulation of hemopoietic colony forming cell differentiation

Through injection of particulate materials and endotoxins (ET), possible control mechanisms of murine hemopoietic colony forming cells (CFC) were investigated. The experimental system employed two inbred strains of mice that responded with a similar increase in splenic CFC after injection of particulate materials, sheep red blood cells (SRBC) and colloidal carbon (CC), but differed in their response to ET. The strains similarly phagocytosed radiolabelled SRBC and ET, suggesting that the CFC changes were not dependent solely on phagocytosis of ET. The CFC from low ET responder strain responded in vitro to colony stimulating factor (CFS) elicited by ET in serum of the high responder strain, demonstrating that lack of response to ET is due, at least in part, to failure to produce CSF. Subjection of serum from either strain to chloroform extraction did not significantly increase its stimulating capacity, suggesting that the increased stimulatory ability in response to ET was due to increase in the CSF level rather than to a decrease in the level of inhibition.