Interferon-alpha induces circulating tumor necrosis factor receptor p55 in humans

In the present studies we investigated the effect of interferon-alpha (IFN alpha) on the release of the soluble (extracellular) form of the tumor necrosis factor p55 receptor (TNFsRp55), because TNFsRp55 is a natural antagonist of tumor necrosis factor (TNF)-induced inflammation and also might be part of the antiinflammatory properties of IFN alpha. Plasma levels of TNFsRp55 were measured by a specific radioimmunoassay in five healthy volunteers and in five patients with chronic hepatitis C treated with IFN alpha. Levels showed a significant increase after a single injection of 5.0 million U IFN alpha in both healthy and hepatitis patient groups. Peak values (3.5 to 4.5 ng/mL) were observed within 12 hours of beginning treatment. Thereafter, levels promptly declined, reaching baseline values within 24 hours. TNF alpha and C-reactive protein (CRP) levels were below the detection limit in the same plasma samples. In addition, IFN alpha suppressed significantly interleukin (IL)-1 alpha-induced TNF alpha protein synthesis by human peripheral blood mononuclear cells. These results suggest that the antiinflammatory properties of IFN alpha may be, in part, also due to the induction and/or release of TNF soluble receptors and the suppression of TNF alpha synthesis.