Retinoic acid acts to neutralize the inhibitory effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on alkaline phosphatase activity of neutrophils that is induced by granulocyte colony-stimulating factor (G-CSF).

Granulocyte colony-stimulating factor (G-CSF) is known to act on the neutrophilic granulocytes from chronic myelogenous leukemia (CML) patients to induce neutrophil alkaline phosphatase (NAP) activity. Gamma-interferon (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been reported to suppress NAP induction with G-CSF. We confirmed that this inhibitory effect of GM-CSF is accompanied by the decrease of the NAP mRNA level. Moreover, we found that the simultaneous addition of retinoic acid completely neutralized this inhibitory effect of GM-CSF. Recovery of the NAP activity brought about by the retinoic acid was also accompanied by the increase of NAP mRNA level. These results indicate that retinoic acid neutralizes the inhibitory effect of GM-CSF on the induction of NAP activity through the change of the NAP mRNA level.