The frequencies of Foxp3+ regulatory T cells in livers and peripheral blood of type I autoimmune hepatitis patients correlate with inflammatory activity

Abstract

The pathogenesis of autoimmune hepatitis (AIH) is not clear. In pediatric patients with type II AIH, a reduced frequency and function of CD4+CD25+Foxp3+ regulatory T cells (Treg) has been reported (1). However, the role of Treg in type I AIH is unclear. Here we analysed the percentage of Treg in the peripheral blood of 26 type I AIH patients, of whom 11 were analysed at diagnosis before treatment initiation, and of 19 healthy donors. To restrict analysis to define Treg and not activated CD4+ T cells, we counted only CD4+CD25highCD127lowFoxp3+ cells as Treg. We found that Treg frequency did not significantly differ in AIH patients at diagnosis (median frequency: 3.6%; 95% CI: 1.92–4.99%), AIH patients under therapy (median frequency 2.0%; 95% CI: 1.76–2.63%; P=0.2536), or healthy blood donors (median frequency: 2.3%; 95% CI: 2.3–3.68%; P=0.9875). To confirm these findings, we assessed the methylation status of the Foxp3 gene locus in CD4+ T cells of healthy subjects and AIH patients. We found that AIH patients under therapy had a similar frequency of demethylated Foxp3 genes (1.6%) as healthy controls (1.7%); whereas AIH patients at diagnosis had 2.4% demethylated loci. Furthermore, we assessed histological Foxp3 staining and inflammatory activity of type I AIH patients in liver biopsies at diagnosis, and found that AIH patients had significantly increased frequencies of Foxp3+ T cells in portal fields (388 cells per mm2 vs. 58 cells per mm2 in NASH patients biopsies; p<0.05); moreover, the histological Foxp3 frequency correlated with inflammatory activity. In contrast to the reported findings in type II AIH, our findings indicated 1) that patients with type I AIH do not have decreased Treg frequencies, and 2) that the Treg frequencies of AIH patients seem to correlate with inflammatory histological activity and decrease under therapy. Thus, it is unlikely that the pathogenesis of type I AIH can be explained by a defective Treg compartment.