Expression and significance of Th22 cells and its functional factor interleukin-22 in mice with autoimmune hepatitis

Objective To investigate the expression of Th22 cells and its functional factor interleukin-22 ( IL-22) in a mouse model of autoimmune hepatitis ( AIH) and the significance of Th22 cells and IL-22 in the pathogenesis of AIH. Methods A total of 30 male C57 BL/6 mice aged 4 weeks were randomly divided into control group with 6 mice and AIH group with 14 mice. Another 10 mice were used to extract liver-specific antigen S100. On days 1 and 7 of the experiment, the freshly extracted S100 was injected into the abdominal cavity of the mice together with an equal volume of Freund's complete adjuvant, and a mouse model of AIH was successfully established on day 28 ( 7 mice in the AIH group died during model establishment due to improper injection, presence of ascites, or infection) . The mice were given intraperitoneal injection of 5% chloral hydrate ( 0. 1 ml/10 g) for anesthesia, and then eyeballs were removed to collect blood samples.The spleen was collected, and flow cytometry was performed to measure the percentage of Th22 cells and RT-PCR was performed to measure the mRNA expression of aryl hydrocarbon receptor ( AHR) . The liver tissue was collected; HE staining was used to observe liver pathological changes, and RT-PCR and Western blotting were used to measure the expression of IL-22 and IL-22 receptor ( IL-22 R) in liver tissue. ELISA was used to measure the serum level of IL-22. The t-test was used for comparison between the two groups. Results HE staining showed that the mice in the control group had well-arranged liver tissue and clear structures of hepatic lobules, while those in the AIH group had massive inflammatory cell infiltration in the portal area and dotted and even piecemeal necrosis in liver tissue. The AIH group had a significant increase in the percentage of Th22 cells than the control group ( 0. 083% ± 0. 052% vs 1. 555% ± 0. 812%, t =-4. 405, P < 0. 05) . Compared with the control group, the AIH group had a significant increase in the relative mRNA expression of AHR ( 0. 485 ±0. 096 vs 1. 268 ± 0. 366, t =-5. 452, P < 0. 05) . Compared with the control group, the AIH group had significant increases in the relative mRNA expression of IL-22 ( 1. 146 ± 0. 227 vs 3. 813 ± 0. 478, t =-12. 458, P < 0. 001) and IL-22 R ( 0. 276 ± 0. 037 vs 1. 734 ±0. 248, t =-15. 333, P < 0. 001) and significantly higher relative protein expression of IL-22 ( 1. 040 ± 0. 261 vs 0. 410 ± 0. 077, t =-6. 324, P < 0. 05) and IL-22 R ( 1. 432 ± 0. 304 vs 0. 830 ± 0. 146, t =-0. 631, P < 0. 05) in liver tissue. The AIH group had a significantly higher level of IL-22 than the control group ( t =-15. 799, P < 0. 05) . Conclusion AIH mice have significant increases in the percentage of Th22 cells and the expression of IL-22, which may play an important role in the pathogenesis of AIH.