Granulocyte-macrophage colony-stimulating factor stimulates human monocyte accessory cell function.

We investigated the effect of recombinant human granulocyte-macrophage CSF (rhGM-CSF) on the accessory cell function of purified human monocytes. Compared with untreated monocytes, rhGM-CSF-treated monocytes promoted enhanced mitogen- and Ag-stimulated lymphocyte proliferation. This enhancement was significantly inhibited by mAb to rhGM-CSF. In experiments designed to define the mechanism of rhGM-CSF augmentation of accessory cell function, rhGM-CSF was shown to cause a dose-dependent increase in monocyte expression of surface HLA-DR molecules and stimulated secretion of IL-1, both important in monocyte T cell interactions. Further studies demonstrated that levels of HLA-DR and IL-1 mRNA were increased by rhGM-CSF, indicating transcriptional regulation of gene expression for HLA-DR and IL-1. Thus, rhGM-CSF augments accessory cell function by human monocytes, and this augmentation correlates with rhGM-CSF-induced increases in transcription of the HLA-DR and IL-1 genes leading to increased expression of surface HLA-DR and secretion of IL-1.