Aberrant Subsets of Regulatory T Cells and their Correlations with Serum IL-2 in Patients with Rheumatoid Arthritis

Aberrant number and/or dysfunction of regulatory T cells (Tregs) is associated with the development of rheumatoid arthritis (RA). This study aimed to assess the frequencies of naive Tregs (nTregs) and memory Tregs (mTregs) in the peripheral blood of RA patients and to explore their relationships with cytokine levels. This study involved 97 RA patients categorized into three groups based on Disease Activity Score 28 (DAS28) and 50 healthy controls (HCs). Flow cytometry was employed to quantify Treg subsets in peripheral blood, while serum cytokine concentrations were measured using a flow cytometry bead array. The findings revealed that three RA groups, stratified by disease activity, all exhibited a significant decrease in both the count and percentage of nTregs and an increase in the percentage of mTregs compared to HCs. Notably, the group with high RA disease activity displayed a higher percentage of mTregs than the remission group. Additionally, correlation analysis indicated that IL-2 concentrations were negatively correlated with total T, CD4 + T and Th17 cell counts, and positively correlated with the absolute count of nTregs. This study demonstrated that the count of mTregs in RA patients increased with escalating disease activity, while the count of nTregs remained unchanged. Moreover, IL-2 concentrations were positively correlated with the numbers of Tregs and nTregs, suggesting that IL-2 plays a significant role in modulating Treg subsets. Further studies on targeted therapies aligned with the distribution of mTregs and nTregs in RA patients with varying disease activity could potentially achieve effective remission.