Intrahepatic IL-8 producing Foxp3⁺CD4⁺ regulatory T cells and fibrogenesis in chronic hepatitis C

Abstract

Background & aims: Regulatory CD4(+) T cells (Tregs) are considered to affect outcomes of HCV infection, because they increase in number during chronic hepatitis C and can suppress T-cell functions.

Methods: Using microarray analysis, in situ immunofluorescence, ELISA, and flowcytometry, we characterised functional differentiation and localisation of adaptive Tregs in patients with chronic hepatitis C.

Results: We found substantial upregulation of IL-8 in Foxp3(+)CD4(+) Tregs from chronic hepatitis C. Activated GARP-positive IL-8(+) Tregs were particularly enriched in livers of patients with chronic hepatitis C in close proximity to areas of fibrosis and their numbers were correlated with the stage of fibrosis. Moreover, Tregs induced upregulation of profibrogenic markers TIMP1, MMP2, TGF-beta1, alpha-SMA, collagen, and CCL2 in primary human hepatic stellate cells (HSC). HSC activation, but not Treg suppressor function, was blocked by adding a neutralizing IL-8 antibody.

Conclusions: Our studies identified Foxp3(+)CD4(+) Tregs as an additional intrahepatic source of IL-8 in chronic hepatitis C acting on HSC. Thus, Foxp3(+)CD4(+) Tregs in chronic hepatitis C have acquired differentiation as regulators of fibrogenesis in addition to suppressing local immune responses.

Keywords: CCL2; Fibrogenesis; Foxp3; GARP; HCV; HSC; Hepatic stellate cells; Hepatitis C virus; IL-8; MMP2; RT-PCR; Regulatory T cells; T effector cells; TIMP1; Teffs; Tregs; alpha-SMA; alpha-smooth muscle actin; chemokine ligand 2; forkhead box P3; glycoprotein A repetitions predimonant; hepatitis C virus; mRNA; matrix metalloproteinases 2; messenger RNA; primary human hepatic stellate cells; real-time polymerase chain reaction; regulatory CD4(+) T cells; tissue inhibitor of metalloproteinases 1.