Bone marrow endogenous colony stimulating factor(s): relation to granulopoiesis in vivo.

Granulocyte-macrophage colony stimulating factors (CSF) are produced both in peripheral tissues and within the bone marrow. Stimulators from either source might regulate granulocyte and monocyte production in vivo. The purpose of this study was to devise an assay for bone marrow endogenous CSF so that its role in regulation of granulopoiesis might be assessed. There was a significant positive correlation between the endogenous CSF level and the subsequent trend in peripheral blood neutrophil count in both normal and infected patients, suggestive of a regulatory role. In addition, granulopoietic recovery after neutropenia was associated with increased endogenous CSF levels. There are two candidate regulators of endogenous CSF production, a stimulatory humoral factor and a neutrophil derived inhibitor which inhibits endogenous CSF production in vitro. Our results suggest that the marrow neutrophil level had a much more significant inhibitory effect than the neutrophil level in the culture.