Background Different subsets of T regulatory (Treg) cells have been described, including Foxp3+ Treg lymphocytes (pTreg, tTreg, and iTreg cells) and Tr1, Th3 and Tr35 cells. In addition, both in mice and humans an apparently novel subset of Treg lymphocytes has been recently described, characterized by the constitutive expression of CD69 [1,2]. In this regard, it has been reported that CD4⁺CD69⁺Foxp3^-TGF-β⁺ cells with a variable expression of CD25 are detected in the peripheral blood and different lymphoid tissues. In mice, these cells exert an important suppressive effect on the immune response, and in humans it has been reported increased levels of these lymphocytes in patients with liver carcinoma, which correlate with tumor size or the presence of metastases. However, this novel Treg cell subset has not been studied in patients with autoimmune inflammatory conditions.

Objectives The aim of this work was to assess the levels and function of the CD69⁺ Treg cells in patients with rheumatoid arthritis

Methods Blood samples were obtained from thirty patients with rheumatoid arthritis (RA) and twenty-five healthy donors. Peripheral blood mononuclear cells were isolated by Ficoll-Hypaque density-gradient centrifugation and stained with the following monoclonal antibodies: CD4/FITC, CD4/APC-Cy7, CD25/APC-Cy7, NKG2D/FITC, LAP (TGF-b)/PerCp-Cy5.5, CD69/APC, IL-10/PE and Foxp3/PE-Cy7. Cells were analyzed by multi-parametric flow cytometry by using the FlowJo software v10. The suppressive function of CD69⁺ cells was assessed by an assay of inhibition of cell activation, measuring the expression of CD40L [3,4] by flow cytometry.

Results We detected increased levels of the CD4⁺CD69⁺CD25^varFoxp3^-LAP⁺IL-10⁺ Treg cells in the peripheral blood of the patients with rheumatoid arthritis in comparison to healthy subjects (p<0.01). In contrast, a deficient suppressor function of these cells was observed in these patients (p<0.05 compared to healthy controls)

Conclusions Our data suggest that the abnormal function of CD69⁺ Treg lymphocytes observed in patients with RA may contribute to the pathogenesis of this condition. The enhanced levels of these cells in the peripheral blood of RA patients are an interesting finding that deserves additional studies

References

1. Gandhi R, Farez MF, Wang Y, Kozoriz D, Quintana FJ, Weiner HL. Human latency- associated peptide⁺ T cells: a novel regulatory T cell subset. J Immunol 2010; 184:4620-4624.

2. Han Y, Guo Q, Zhang M, Chen Z, Cao X. CD69⁺CD4⁺CD25^- T cells, a new subset of regulatory T cells, suppress T cell proliferation through membrane-bound TGF-β1. J Immunol 2009; 182:111-20.

3. Canavan JB, Afzali B, Scottà C, Fazekasova H, Edozie FC, Macdonald TT, Hernandez-Fuentes MP, Lombardi G, Lord GM. A rapid diagnostic test for human regulatory T-cell function to enable regulatory T-cell therapy. Blood Journal 2012; 119:57-66.

4. Chattopadhyay PK, Yu J, Roederer M. A live-cell assay to detect antigen-specific CD4+ T cells with diverse cytokines profiles. Nat Med 2005; 11:1113-1117

Disclosure of Interest None declared