Reduced FOXP3(+) regulatory T cells in patients with primary sclerosing cholangitis are associated with IL2RA gene polymorphisms.

BACKGROUND & AIMS: Recently, genome wide association studies in primary sclerosing cholangitis (PSC) revealed associations with gene polymorphisms that potentially could affect the function of regulatory T cells (Treg). The aim of this study was to investigate Treg in patients with PSC and to associate their numbers with relevant gene polymorphisms. METHODS: Treg frequency in blood was assessed by staining for CD4(+)CD25(high)FOXP3(+)CD127(low) lymphocytes and determination of Treg-specific FOXP3 gene locus demethylation. Single nucleotide polymorphisms (SNP) in the interleukin-2 receptor alpha (IL2RA), the interleukin-2 (IL2) and interleukin-21 (IL21) gene locus were analysed. Liver biopsies taken at the time of diagnosis were stained for FOXP3 and CD3. Treg function was assessed in a CFSE-based suppression assay. RESULTS: The frequency of Treg in peripheral blood of PSC patients was significantly decreased. We confirmed this finding by demonstrating a reduction of non-methylated DNA in the Treg-specific demethylated FOXP3 gene region of peripheral blood cells in PSC patients. Reduced peripheral Treg numbers were significantly associated with homozygosity for the major allele of the SNP "rs10905718" in the IL2RA gene. Intrahepatic FOXP3(+) cell numbers at the time of initial diagnosis were decreased in PSC as compared to PBC. In addition to reduced numbers, the suppressive capacity of Treg isolated from PSC patients seemed to be impaired as compared to healthy controls. CONCLUSIONS: Our findings indicate that Treg impairment may play a role in the immune dysregulation observed in PSC. Reduced Treg numbers in patients with PSC are associated with polymorphisms in the IL2RA gene.

FOXP3+ regulatory T cells in autoimmune hepatitis are fully functional and not reduced in frequency.

BACKGROUND & AIMS: The pathogenesis of autoimmune hepatitis (AIH) is not understood, but it was suggested that AIH may be related to a numerical or functional impairment of CD4+CD25+FOXP3+ regulatory T cells (Treg), which are important mediators of immune tolerance to self-antigens. However, the role of Treg in AIH is not clear, since earlier studies reporting Treg impairment had used only CD25 as marker that cannot unambiguously distinguish Treg from activated effector T cells. METHODS: We assessed the frequency and suppressor function of Treg using current staining protocols that can distinguish Treg from activated effector T cells. RESULTS: The frequency of CD4+CD25(high)CD127(low)FOXP3+ Treg cells in blood of AIH patients was not reduced compared to healthy subjects, as shown by flow cytometry and confirmed by quantifying Treg-specific demethylation of the FOXP3 gene. Moreover, the suppressor function of Treg isolated from AIH patients was similar to that of Treg isolated from healthy subjects, indicating that Treg function was not impaired in AIH patients. However, we observed that the Treg frequency was significantly higher in those AIH patients with active disease than in those who were in a state of remission, suggesting that the Treg frequency may increase with the degree of inflammation. Indeed, analysis of FOXP3+ Treg in liver histology revealed that the intrahepatic Treg frequency was higher in AIH patients than in NASH patients and correlated with the inflammatory activity of the liver. CONCLUSIONS: The frequency and function of circulating Treg cells is not impaired in AIH.