Genetic association of cytokines polymorphisms with autoimmune hepatitis and primary biliary cirrhosis in the Chinese

AIM: To characterize gene polymorphism of several cytokine gene in-patients with AIH and PBC and to analyze the difference of the polymorphism distribution between Chinese patients and healthy controls. METHODS: The study population consisted of 62 patients with AIH, and 77 patients with PBC. The genetic profile of four cytokines was analyzed by restriction fragment length polymorphism after specific PCR amplification (PCR-RFLP) or sequence-specific primers PCR (SSP-PCR). The analyzed gene polymorphism included interleukin-1 (IL-1) (at position +3 953 and IL-1RN intron 2), IL-6 (at position -174), IL-10 promoter (at position -1082, -819, and -592). The control group consisted of 160 healthy blood donors. RESULTS: The majority of Chinese people including patients and healthy controls exhibited IL-1B 1,1 genotype, and there was no significant difference in AIH, PBC patients and controls. There were highly statistically significant differences in the distribution of the IL-1RN gene polymorphism between the patients with PBC compared with controls. The frequency of IL-1RN 1,1 was significantly higher (90.9% vs 79.4%, P=0.03) and the frequency of IL-1RN 1,2 was significantly lower in PBC patients (6.5% vs 17.5%, P=0.01). No statistical difference was observed between AIH patients and controls. All of the 160 healthy controls and 62 cases of AIH patients exhibited IL-6-174GG genotype, and there were four cases, which expressed IL-6-174GC genotype in 77 cases of PBC patients. The frequency of IL-6-174GC was markedly significantly higher in PBC patients compared with controls (5.2% vs 0%, P=0.004). No statistically significant difference was found in the distribution of IL-10 promoter genotype in AIH and PBC patients compared with controls. CONCLUSION: The polymorphisms of IL-1RN and IL-6-174G/C appear to be associated with PBC in Chinese patients.