Deficient or abundant but unable to fight? Estimation of circulating FoxP3+ T regulatory cells and their counteracting FoxP3− in rheumatoid arthritis and correlation with disease activity

Potential of neutrophil to lymphocyte ratio in predicting sustained remission in rheumatoid arthritis compared to other immune activation markers

Background & objectives:

Cells and cell proportions may indicate the equilibrium status of the immune system. The present study was conducted to evaluate the role of cytokines and the immunocompetent cells as biomarkers of remission in rheumatoid arthritis (RA) patients intended to withdraw or reduce disease-modifying anti-rheumatic drug (DMARD) treatment.

Methods:

This prospective observational study involved newly diagnosed and treated RA patients who fulfilled 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) criteria. The patients were classified based on disease activity score (DAS)28-C-reactive protein (CRP)(3) score into remission (≤2.6) and treatment-naïve/active (>2.6) groups. Remission patients were followed up for six months and were reclassified into those in sustained remission (≤2.6) and relapse (>2.6) based on the DAS28-CRP(3) score. Various cytokines and cell surface markers were quantitated using whole blood samples, and the CD3⁺/CD19⁺ and FOXP3⁺/CD4⁺ ratios were calculated. The clinical, demographic, cytokine and cellular phenotype characteristics were compared between remission and treatment-naïve groups. The factors associated with sustained remission were verified.

Results:

Of the 72 patients, 52 were in remission and 20 were DMARD naïve and had active disease. Duration of illness, interleukin-6 (IL-6) and IL-10 were significantly different between remission and treatment naïve/active disease patients. Increased likelihood for achieving sustained remission was noted in RA patients with baseline NLR ≤2. Other demographic/clinical variables and cell phenotypes, namely age, gender, duration of illness, CD3⁺, CD4⁺, FOXP3⁺, CD19⁺, CD3⁺/CD19⁺, FOXP3⁺/CD4⁺ and cytokines - IL-6 and IL-10 were not associated with sustained remission.

Interpretation & conclusions:

The present preliminary study highlighted the potential of NLR in predicting sustained remission in RA patients with a cut-off <2. Further study with a large sample size should be done to confirm this finding.

T-regulatory cells from patients with rheumatoid arthritis retain suppressor functions in vitro

Rheumatoid arthritis (RA) is a chronic disease of connective tissue caused by intolerance to self-antigens. Regulatory T cells (Tregs) are key players in maintaining autotolerance through a variety of suppressor mechanisms. RA is generally believed to develop due to disorders in Tregs; however, there is no consensus on this issue. Thus, the present study focused on phenotypical analysis of Treg cells and their ability to suppress CD4⁺ and CD8⁺ cell proliferation. The present study used peripheral blood samples from 21 patients with RA and 22 healthy donors. The CD25⁺FoxP3⁺ subpopulation of Tregs was analyzed using flow cytometry to evaluate the expression of CTLA-4, PD-L1, HLA-DR, CCR4, CD86 and RORyt. Tregs suppressor activity was calculated in terms of suppression of the proliferation of CD4⁺ and CD8⁺ lymphocytes in vitro. Suppressor activity of the total Treg population did not differ between patients with RA and healthy donors. However, the patients had elevated CD25^loFoxP3⁺ levels and lower CD25^hiFoxP3⁺ levels; in addition, they had more activated Tregs expressing PD-L1, HLA-DR, CCR4 and CD86. The surface expression of CTLA-4 was below the reference level. The patients also had transitional FoxP3⁺RORyt⁺ cells and elevated CD4⁺RORyt⁺ levels, which were highly correlated with disease activity. These results show that in RA, Treg cells are activated and have an immunosuppressive activity. However, it is the transitional FoxP3⁺RORyt⁺ cells and increased CD4⁺RORyt⁺ percentages in peripheral blood that appear to be associated with the pathological conversion of some Treg cells into Th-17. This process appears to be key in RA pathogenesis.

Inhibitory activity of FOXP3+ regulatory T cells reveals high specificity for displaying immune tolerance in remission state rheumatoid arthritis

Immune regulation status may indicate immunological remission in rheumatoid arthritis (RA). This cross-sectional study aimed to determine the Regulatory T cell (Treg) properties, together with 14 plasma cytokines levels between active RA and clinical remission patients. Peripheral blood (PB) Foxp3+ Treg was collected from RA patients for determination of Treg inhibitory activity using a co-culture system. Other PB T cell types and plasma cytokines were determined by flow-cytometry. The Treg results were analyzed according to the disease activity score-28 (DAS28). Then sensitivity and specificity were calculated for the indication of the remission status. The number and inhibitory activity of Treg are higher in the clinical remission as compared to the active RA (p value < 0.0001). Also, Treg: CD4+CD25+CD127+ cell ratio demonstrates the similar result (p value < 0.05). Treg inhibitory activity is inversely correlated with the DAS28. Specificity and positive likelihood ratio of inhibitory activity for indicating remission status are 92.31% (95% CI 63.97-99.81) and 11.14 (95% CI 1.67-74.14), respectively. Treg inhibitory activity is a promising prognostic marker and probably represents the immunological remission status in RA.

The Proportion of Regulatory T Cells in Patients with Rheumatoid Arthritis: A Meta-Analysis

Background

Regulatory T cells (Tregs) have important functions in peripheral immune tolerance. Dysfunction of Tregs is considered to be a pivotal cause of autoimmune diseases, including rheumatoid arthritis (RA). However, previous reports describing the proportion of Tregs among CD4⁺ T cells in RA patients were controversial because a range of markers are used to identify Tregs with little consensus. To clarify the status of Tregs in RA, we investigated the proportion of Tregs with focusing on the definitions of them.

Methods

We identified the studies reporting the proportion of Tregs in RA patients using PubMed and Google Scholar. We performed a systematic review of them and a meta-analysis to evaluate the proportion of Tregs (FOXP3-positive and/or CD25-positive) among CD4⁺ T cells in peripheral blood (PB) and synovial fluid (SF) of RA patients and control subjects.

Results

A total 31 studies were selected. The proportion of Tregs defined by all definitions among CD4⁺ T cells in PB was not significantly different between RA patients and control subjects (-0.65, [-1.30, 0.01]). Then we performed sub-analyses based on individual definitions. The proportion of Tregs defined by either CD25 or FOXP3 alone did not differ between RA patients and control subjects. The proportion of Tregs defined by both FOXP3 and CD25 was lower in RA patients than that in control subjects (-2.42 [-3.49, -1.34]). The proportion of Tregs defined by both FOXP3 and CD25 was higher in SF than that in PB among RA patients (3.27 [0.40, 6.14]).

Conclusion

The status of Tregs varied according to the definition system. The proportion of Tregs defined by stricter and functionally validated methods decreased in PB and increased in SF among RA patients. If the proportion of Tregs differs in RA, accurate and functionally relevant definitions of Tregs are necessary to elucidate their status in RA.