Effects of granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-2, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and IL-6 on the production of immunoreactive IL-1 and TNF-alpha by human monocytes.

The effects of GM-CSF, IL-2, IFN-gamma, TNF-alpha and IL-6 on the production of IL-1 (both secreted and cell associated) and TNF-alpha by peripheral blood monocytes were studied. Monocytes were cultured for 20 h in suspension and in serum-free conditions which minimized background stimulation of monokine production. GM-CSF, IL-2 and TNF-alpha directly induced the production of cell-associated IL-1 but little or no IL-1 or TNF-alpha secretion. Combination of GM-CSF with IFN-gamma, IL-2 or TNF-alpha synergistically enhanced IL-1 secretion and had an additive effect on cell-associated IL-1 production. Combination of IL-2 with IFN-gamma or TNF-alpha also synergistically enhanced IL-1 secretion but the effect on cell-associated IL-1 production was less than additive. GM-CSF synergistically enhanced TNF-alpha secretion induced by IFN-gamma but not by lipopolysaccharide. GM-CSF did not enhance TNF-alpha secretion induced by IL-2 or TNF-alpha. In contrast, IL-2 synergistically enhanced TNF-alpha secretion induced by IFN-gamma. These results are discussed in relation to cytokine involvement in rheumatoid arthritis.