Imbalance between T helper type 17 and T regulatory cells in patients with primary biliary cirrhosis: the serum cytokine profile and peripheral cell population

Abstract

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune liver disease characterized by progressive loss of intrahepatic small bile ducts. Cellular immune mechanisms involving T cell reaction are thought to be involved significantly in the pathogenesis of PBC. Recent studies have independently revealed enhanced T helper type 17 (Th17) response and weakened T regulatory cell (T(reg)) response in some autoimmune diseases, indicating a role of Th17/T(reg) imbalance in the pathogenesis of autoimmunity. This prompted us to investigate whether the Th17/T(reg) balance was broken in the peripheral blood of patients with PBC and, if it was, what cytokine circumstances might contribute to this imbalance. The expression of 11 Th17/T(reg) differentiation-related genes and serum concentrations of the corresponding cytokines in 36 patients with PBC, 28 patients with chronic hepatitis B and 28 healthy controls were measured by real-time quantitative-polymerase chain reaction and enzyme-linked immunosorbent assay respectively. Peripheral Th17 and T(reg) cells were analysed by flow cytometry. Th17-related cytokines were increased significantly in patients with PBC. Consistent with the cytokine profile, the Th17 cell population and retinoid-related orphan receptor gammat expression were increased markedly. In contrast, the T(reg) cell population and forkhead box P3 expression were decreased dramatically in the peripheral blood of patients with PBC. Our study revealed that the Th17/T(reg) imbalance, both cytokine profile and cell numbers, exists in patients with PBC, suggesting its potential role in the breakdown of immune self-tolerance in PBC. Interleukin-23, which characterized the imbalanced cytokine profile, may play an essential role in Th17-related human autoimmunity.

Fig. 1

Expression ratio of T helper type 1 (Th17) and T_reg-related gene in patients with primary biliary cirrhosis (PBC). When compared with healthy controls (HC), Th17-related genes were up-regulated significantly (a), whereas transforming growth factor (TGF)-β1 and forkhead box P3 (FoxP3) were obviously down-regulated (b) in patients with PBC. Comparison between patients with PBC and patients with chronic hepatitis B (CHB) is shown in (c) and (d). Data are presented as the whisker–box plot and analysed by Mann–Whitney U-test. Boxes represent the interquartile range, with the median represented by the line inside the box. Upper whisker, the highest value less than or equal to the 75 percentile plus 1·5 times interquartile range; lower whisker, the lowest value greater than or equal to the 25 percentile minus 1·5 times interquartile range. Outliers were excluded.

Fig. 2

Serum concentration of T helper type 1 (Th17) and T_reg-related cytokines. Interleukin (IL)-1β (a), IL-6 (b), IL-23 (c) and IL-17A (d) were increased in patients with primary biliary cirrhosis (PBC) while transforming growth factor (TGF)-β1 (e) and IL-2 (f) were not changed statistically. Data are presented as mean ± standard deviation and analysed by Mann–Whitney U-test. CHB, chronic hepatitis B; HC, healthy control.

Fig. 3

The population of T helper type 1 (Th17) cells as a percentage of total CD4⁺ cells in the peripheral blood mononuclear cells was evaluated by flow cytometry. Representative plots in patients with primary biliary cirrhosis (PBC), chronic hepatitis B (CHB) and healthy control (HCs) are shown in (a), (b) and (c) respectively. Representative plots of peripheral populations of T regulatory cells in patients with PBC, CHB and HC are shown in (d), (e) and (f) respectively.

Fig. 4

Distribution of T helper type 1 (Th17) (a) and T regulatory cells (b) subset population of subjects in each studied group. The mean cell population for each group is represented by a line. PBC, primary biliary cirrhosis; CHB, chronic hepatitis B; HC, healthy control.