Serum levels of interleukin 17 and its activators in chronic hepatitis C patients

Immune dysregulations in patients with chronic hepatitis C are still poorly understood, particular ly their inflammatory pathways. Recent studies have shown that transforming growth factor β (TGF- β) alone promotes the generation of anti-inflammatory regulatory T lymphocytes (T-reg) from na l ¨ ve T CD4+ cells, while TGF- β in concert with interleukin 6 (IL-6) promotes Th17 cells that produce IL-17. We stud ied serum levels of IL-17 and its known activators (IL-6, TGF- β) in 55 hepatitis C patients and 33 ageand gender-matched healthy subjects. Cytokine levels were quantified by sandwich enzyme-linked immunosorbent assays. Surprisingly, IL-17 serum levels were significantly higher in healthy subjects than in hepatitis C patients (16.5 ±6.6 pg/ml vs. 8.1 ±5.5 pg/ml; p < 0.0000). By contrast, serum TGF- β levels were significantly lower in healthy subjects (30.9 ±7.4 ng/ml vs. 40.7 ±20.6 ng/ml; p = 0.0327). Serum levels of IL-6 did not differ between groups but correlated positively with the stage of fibrosis in hepatitis C patients (r = 0.36; p = 0.005). Our findings suggest that hepatitis C virus downregulates IL-17 production and up-regulates TGF- β production. The increased level of TGF- β in HCV patients may be responsible for suppressing IL-17 production by Th17 cells.