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

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.