Effects of endotoxin on murine erythropoiesis in vitro: role of marrow adherent cells.

Endotoxin injected into experimental mice suppresses marrow erythropoiesis by an as yet unknown mechanism. We have studied the effects of endotoxin added to the methylcellulose culture system for growth of erythroid stem cells (BFU-E). The addition of endotoxin decreased BFU-E growth from murine normal (unseparated) femoral marrow mononuclear cells. This suppressive effect was not seen when most of the adherent cells were removed from the culture system prior to the addition of endotoxin. We speculate that whereas "normal" adherent cells provide a favorable microenvironment for the growth of erythroid stem cells, adherent cells altered by endotoxin either loss their ability to support erythroid growth or suppress erythroid colony formation. These observations may be of relevance to the explanation of the pathogenesis of the anemia of infection of chronic diseases.