Background: Regulatory CD4+ T cells (Tregs) exhibit functional alterations in patients with multiple sclerosis (MS). Transforming growth factor (TGF)-β is a key regulator of Treg development and function.

Objective: The objective of this study is to determine whether the expression of functionally relevant TGF-β-regulated molecules is altered in Tregs from patients with MS.

Methods: Expression of nine Treg markers was analyzed by multi-color flow cytometry in CD4+ T cells and Treg subpopulations of 31 untreated MS patients and age- and sex-matched healthy donors (HDs). Correlations between Treg marker expression and clinical variables were sought.

Results: Expression of the transcription factor Helios, which defines thymic-derived Tregs, was decreased in this Treg subpopulation. The frequency of peripherally generated Tregs was increased in patients with MS, particularly in patients with progressive MS. Low frequencies of thymic-derived Tregs were associated with magnetic resonance imaging (MRI) lesion-burden and a high relapse rate. Four surface markers associated with TGF-β signaling (ABCA1, BTLA, DNAM-1, and GARP) were differentially expressed on Tregs from patients with MS and HDs. Expression levels of CD73, CD103, ABCA1, and PAR2 showed strong correlations with disease severity.

Conclusion: We have identified novel markers abnormally expressed on Tregs from patients with MS that could detect patients with severe disease.