CD4+ CD25+ but not CD4+ Foxp3+ T cells as a regulatory subset in primary biliary cirrhosis

Abstract

Increasing evidence indicates a role for regulatory T cells (Tregs) in the immune response and in autoimmune diseases, but the role of Tregs and cytokines in autoimmune hepatic diseases remains largely unclear and controversial, especially in patients with primary biliary cirrhosis (PBC). This study was undertaken to investigate Tregs and different cytokines in the liver and peripheral blood of PBC patients. We found that these patients demonstrated a reduction of CD4(+)CD25(+) T cells but elevated CD4(+)Foxp3(+) T cells in peripheral blood mononuclear cells (PBMCs) and CD4(+) T cells. The percentage of CD4(+)CD25(+) T cells in PBMCs was negatively correlated with elevated plasma interferon (IFN)-γ levels. A liver-specific analysis showed that the frequency of Foxp3(+) Tregs, transforming growth factor (TGF)-β1 and IFN-γ were increased in PBC patients. Our findings suggest that an imbalance between CD4(+)CD25(+) Tregs and cytotoxic cytokines plays a crucial role in the pathogenesis of PBC while the role of Foxp3 needs further investigation.

Figure 1

Increased CD4⁺Foxp3⁺ cells and decreased CD4⁺CD25⁺ cells in PBC patients. (a) The percentage of CD4⁺Foxp3⁺ or CD4⁺CD25⁺ cells in PBL of PBC patients and controls was analyzed by flow cytometry. (b) The ratios of Foxp3⁺ or CD25⁺ to CD4⁺ T cells in PBC patients were calculated. (c) Representative plots of CD4⁺Foxp3⁺ or CD4⁺CD25⁺ cells in PBL of PBC patients and controls. Foxp3, forkhead box P3; PBC, primary biliary cirrhosis; PBL, peripheral blood lymphocytes.

Figure 2

Negative correlation between the percentage of CD4⁺CD25⁺ cells and the expression of plasma IFN-γ. In PBC patients, correlation between the percentage of CD4⁺CD25⁺ cells (a) or the ratio of CD25⁺ to CD4⁺ T cells (b), and the level of plasma IFN-γ was analyzed by Superman correlation test. IFN, interferon.

Figure 3

Increased expression of Foxp3, TGF-β1 and IFN-γ in liver tissues of PBC patients (×400). Foxp3⁺ T cells were found to be scattered among the lymphocytes infiltration in the portal tracts of PBC patients (a), but no significant Foxp3⁺ T cells were found in healthy livers (b). TGF-β1 mainly localized in the cytoplasm of hepatic cells in PBC patients (c), and also with lower expression in control livers (d). The expression of IFN-γ was found in the sinus space of hepatic cells and surrounding small bile ducts in PBC livers (e), while with no significant expression in healthy livers (f). Foxp3, forkhead box P3; IFN, interferon; PBC, primary biliary cirrhosis; TGF, transforming growth factor; Treg, regulatory T cell.