Endotoxin-induced myeloid reactions in dogs.

The response to artificial endotoxinemia was studied in adult dogs. Granulocyte-macrophage colony stimulating activity (CSA) in lung tissue and blood was measured along with the number of circulating granulocytes and myeloid committed stem cells (colony forming units, CFUc). Acute endotoxinemia induced a measurable CSA increase in lung tissue before being detectable in blood. Granulocytes, rapidly removed from the circulation, showed no release of CSA during sequestration. These experiments demonstrate that the process of endotoxin recognition and subsequent transition into a myelopoietic stimulus is medicated by cells belonging to tissue; mature granulocytes, involved in the defence against bacterial infection, do not release activity that promotes growth of immature myeloid cells.