Introduction In autoimmune hepatitis (AIH) CD4posCD25high regulatory T-cells (T-regs), a subset central to immune-tolerance, are numerically defective and impaired in their ability to control effector cell function. At variance with CD4 effectors, T-regs, classically known as CD25high and FOXP3pos, express low levels of the activation marker CD127. The aim of the current study was to provide a phenotypic and functional profile of CD4posCD25highCD127lowT-regs (CD127lowT-regs) in AIH and to explore to what extent absence or low levels of CD127 impact on T-reg ability to suppress.
Methods 20 ANA/SMA+ AIH patients and 12 healthy subjects (HS) were studied. T-reg phenotype was determined by flow cytometry using antibodies to CD4, CD25, CD127, CTLA-4 and Galectin-9, a molecule linked to T-reg ability to suppress. T-reg transcription factor and cytokine profile were assessed by intracellular staining. CD127lowT-reg ability to suppress was evaluated in a proliferation assay following co-culture with CD25neg target cells.
Results In AIH CD4posCD25high cells contained fewer CD127low cells than in HS. Compared to conventional CD4posCD25high (cT-regs), CD127lowT-regs from both AIH and HS had a) higher numbers of FOXP3pos, CTLA-4pos, Galectin-9pos and IL-10pos cells; b) lower numbers of T-betpos, RORCpos, IFNgpos and IL-17pos cells; and c) similar numbers of TGF-bpos cells. In AIH, CD127lowT-regs contained fewer FOXP3pos, CTLA-4pos, Galectin-9pos, IL-10pos and TGF-bpos cells and higher frequencies of T-betpos, RORCpos, IFNgpos and IL-17pos cells than in HS. CD127lowT-regs inhibited CD25neg cell proliferation more effectively than cT-regs, though less markedly in AIH than in HS. In AIH, treatment with anti-IFNg and anti-IL-17 neutralising antibodies ameliorated the suppressive ability of cT-regs, while leaving unchanged that of CD127lowT-regs; exposure to anti-IL-10 neutralising antibodies reduced cT-reg suppression in HS, but not in AIH.
Conclusion CD127low T-regs bear the phenotypic and functional signature of “true T-regs”. Low numbers and reduced suppressive function of CD127lowT-regs in AIH may contribute to breakdown of immune-tolerance by permitting effector cells to perpetrate hepatocyte damage.
Competing interests None declared.