Marrow culture in diffusion chambers in rabbits: III. Effect of endotoxin and leukocyte products on cell production

Soluble leukocyte products harvested from incubated peritoneal exudate leukocytes, injected intravenously or intramuscularly, increased production of granulocytes and macrophages in marrow in diffusion chambers implanted into the peritoneal cavity of rabbits. Red cell production in the chambers was not consistently affected. Endotoxin increased production of all cell types. Endotoxin tolerance induced by daily injection of endotoxin to host rabbits abolished granulopoietic stimulation by endotoxin given during the culture period but did not diminish the granulopoietic stimulation produced by injected leukocyte products. Attempts to induce tolerance to leukocyte products by daily injections did not reduce the granulopoietic stimulation produced by either endotoxin or leukocyte products injected during the culture period. Intraperitoneally administered leukocytes products markedly inhibited production of all cell types. Endotoxin or leukocyte products given to normal rabbits increased plasma colony stimulating activity (CSA); the increase occurred sooner after leukocyte products than after endotoxin. Endotoxin‐tolerant animals showed no rise in CSA after endotoxin, but their response to leukocyte products was normal. Leukocyte products added to agar cultures neither supported nor inhibited colony growth but augmented CSA‐stimulated colony production. Endotoxin, leukocyte products, and CSA are different and may interact in regulating granulopoiesis.