The Immune Modulation And Mechanism Of Regulatory T Cells In Primary Biliary Cirrhosis

Backgrouds:Primary biliary cirrhosis (PBC) is an autoimmune liver disease, of which the morbidity in elderly women is highest. It is characterized by progression of interlobular bile duct damage, elevated serum alkaline phosphatase and IgM level. And multiple autoantibodies are positive, of which the antimitochondrial antibody type 2 is the most specific. Regulatory T cell (Treg) is an important cell for modulation and controls the immune responses, which plays a crucial role in immune tolerance and dynamic balance. In health, Tregs have the capacity of suppression autoimmune reaction in the liver. However, immune tolerance is broken when the number and function of Tregs is impaired. CD3+cells consist of Natural killer T (NKT, CD3+, CD56+) and CD3+CD56T-cells. It was reported that NKT cells can promote autoimmune reaction, which could be related to destruction of the balance of Th1/Th2 type reaction and regulation the secretion of cytokines. To investigate the role and relationship of these cells on the pathogenesis of PBC, we detected the cytokine levels and the distribution of lymphocytes in the patients, and studied functional characteristics by in vitro experiments, aiming to find a potential immune mechanism of PBC.Methods:Collect and analyze the clinical data. Detect the number and the proportion of Tregs and NKT cells by flow cytometry and levels of cytokines by enzyme-linked immune response (ELISA). Isolate mononuclear cells for studying the function by in vitro experiments.Results:Part1 Results showed that the number of Tregs in patients with PBC and the production of Interleukin-10 (IL-10) were both decreased significantly; Tregs from patients with PBC are ineffective to suppress T cell proliferation and the production of interferon-y (IFN-y), and inhibition of cytotoxicity capability against bile duct epithelial cells is possibly lower than the healthy controls; In addition, costimulatory molecules CD80/CD86 on the DC in the patients with PBC significantly were higher than healthy controls which were more pronounced after the stimulation; inhibition of a-smooth muscle actin (α-SMA) expression by human hepatic stellate cells was inefficient; Inhibition of CD86 expression on the DC by Treg was significantly weakened in the patients with PBC.Part2 The results found that the proporition of CD3+ CD56+ NKT cells showed a marked increase in the patients with PBC, whereas CD3+CD56T- cells showed no difference in the percentage between these two groups; IL-17 and its related cytokines in plasma were increased in the patients with PBC; In addition, IL-17 prodution by CD3+ CD56+ of NKT cells was significantly higher than other cells; Besides, level of IL-17 in the supernatant was significantly increased with autoantibodies stimuli from the patients with PBC, and the main origin were CD3+ CD56+ of NKT cells; IL-17 could activate hepatic stellate cells by promoting production transforming growth factor β (TGF-β) and the expression of alpha SMA, and showed a dose dependent; Activation of hepatic stellate cells was more significant with higher levels of TGF-β and expression of a-SMA in the patients with PBC.Conclusions:In the process of PBC, the impaired Treg was declined in number, proportion and function, which contributed to ineffective ability to inhibiting the dendritic cell activation and inflammation; Besides, levels of IL-17 production by NKT cells was higher with stimulation, which promoted activation of hepatic stellate cell. Treg showed a deficient suppression on proinflammatory of NKT cells, which lead to advance of hepatic fibrosis.