Circulating levels of interferon-gamma in course of hepatitis C virus-related arthritis.

The aim was to weigh the serum concentrations of interferon gamma (IFN-gamma), a cytokine that enhances Th1-cell differentiation and suppresses collagen synthesis and angiogenesis, in two apparently distinct diseases, hepatitis C virus-related arthritis (HCVrA) and rheumatoid arthritis (RA), which share some overlapping immunological features. In this study, IFN-gamma serum levels were assayed by an ELISA method in 21 HCVrA patients and in 16 with RA. Very low IFN-gamma serum levels were found in five out of 21 patients with HCVrA and only in three out of 16 RA patients. Median value (range) resulted decrease in both HCVrA and RA groups, that is, 0.29 (0.04-1.49) versus 0.20 (0.05-1.18) IU/mL, P = 0.58. No correlation was evidenced with hepatic and arthritic involvements, nor between IFN-gamma serum levels and viral replication and moreover with the positivity of antinuclear antibody, rheumatoid factor, and anti-cyclic citrullinated peptides antibodies. These results show that IFN-gamma behavior appears similar in HCVrA and RA groups reinforcing the lack of significant differences between HCVrA and RA patients. Low circulating levels could be explained with the fact that IFN-gamma is not an isolate cytokine, but a piece of composite system regulated in a complex fashion, with many different factors contributing.