PAF AND HEMATOPOIESIS .10. MACROPHAGE-COLONY-STIMULATING FACTOR AND GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR ENHANCE PLATELET-ACTIVATING-FACTOR ACETYLHYDROLASE PRODUCTION BY HUMAN BLOOD-DERIVED MACROPHAGES

Platelet-activating factor (PAF), a phospholipid autacoid with potent regulatory functions, is synthesized by stimulated monocytes. Macropha ges are a source of the plasma acetylhydrolase activity (AHA) which re gulates PAF concentrations. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF) are i nvolved in the differentiation and functions of cells from the monocyt ic/macrophagic lineage. This work reports that M-CSF and GM-CSF stimul ated AHA production by human blood monocyte-derived macrophages in a t ime- and dose-dependent manner. After 7 days of culture without serum, a 6- and 4-fold increase was found in cells treated with M-CSF (1000 U/ml) and CM-CSF (50 ng/ml), respectively. M-CSF (up to 1000 U/ml) and GM-CSF (up to 10 ng/ml) did not induce PAF production by human blood monocytes. While GM-CSF (10 ng/ml) and interleukin-1 (10 U/ml) stimula ted M-CSF production from monocyte-derived macrophages, PAF did not. T hese results indicate that M-CSF and GM-CSF enhance AHA production by human blood-derived macrophages cultured in low serum concentrations. Clearly the effects of growth factors on AHA production in vivo deserv e to be assessed.