Th17 and IL-17 immunity in chronic hepatitis C infection.

Hepatitis C virus (HCV) is one of the most important etiologic agents of postransfusional hepatitis and a common cause of chronic hepatitis, cirrhosis and hepatocarcinoma. T helper (Th)17 cells are a newly discovered Th cell subset with implications in both host defense and autoimmunity. Th17 implications in chronic HCV infection are not well characterized. Given the important role in multiple other immune and inflammatory conditions, they are of obvious interest. Specific HCV-Th17 cells are implicated in immune response modulation, correlated with fibrosis severity and intrahepatic inflammatory status. Serum IL-17 levels are higher in chronic HCV infected patients and Th17 cytokines are modulated within the therapeutic response at anti-viral treatment. However, novel intriguing data indicate that Th17 boost could be associated with spontaneous HCV clearance. It is possible that Th17 could play a dual role (both beneficial and harmful) and that an unbalance of regulating factors (chemokines, transcription factors, receptor expression, etc.) rather than the lymphocyte itself could tip the Th17 immune response one way or another. The role of Th17 cells in host anti HCV defense is beginning to emerge and one has to focus upon its potential beneficial aspects and not only on its destructive potential.