Background/Purpose:

 Immune unbalance between Th17 and regulatory T cells (Treg) is a characteristic of systemic sclerosis (SSc). The functional heterogeneity and differentiation dynamics can be clearly shown by separating Treg cells into three subsets based on the expression of FoxP₃and CD45RA. The aim of this study was to investigate subsets levels of Treg from the patients with naive SSc and assess their roles in the immune balance between Treg and Th17.

Methods:

Peripheral blood from 31 patients with SSc and 33 health controls were collected. Peripheral blood mononuclear cells (PBMCs) were prepared and analyzed for the expression of CD4, CD25, CD45RA, CTLA-4, CD69, CD279, GITR, FoxP3 and IL-17 with flow cytometry. Measuring Treg suppressive capacity against proliferation of CD4⁺CD25^– T cells in coculture experiments by a CFSE based. The expression of FoxP₃, CTLA-4, IL-17A and RORC mRNA were studied with real-time PCR.

Results:

(1)The frequency of CD4⁺CD25⁺FoxP₃⁺Treg cells were significantly elevated in patients with SSc (3.62±1.14) compared with controls (1.97±0.75, P<0.001), but the expression of CTLA-4 and its mRNA were lower in Treg cells of SSc patients compared with control with diminished immunosuppression capacity.

 (2) In the patients with SSc, the frequency of CD45RA^–FoxP₃^high activated Treg cells (aTreg,FrII) were lower than control (0.25±0.16 vs 0.66±0.41 among CD4+, P<0.001; 12.42±5.23 vs 30.01±1.74 among Treg, P<0.001),CD45RA^–FoxP3^lo T cell (FrIII) were higher than control(6.23±2.29 vs 2.90±0.91 among CD4+, P<0.001; 73.71±9.62 vs 57.96±9.90 among Treg, P<0.001),There were no significant difference in two groups with CD45RA⁺FoxP3^loTreg cells (rTreg,FrI),which were relatively lower in Treg cells (1.87±0.94 vs 1.63±0.97 among CD4+, P=0.320; 23.19±10.60 vs 29.63±11.77 among Treg, P=0.025).

(3)In the patients with SSc, immunosuppressive capacity of aTreg and rTreg cells were diminished,FrIII cells had no immunosuppressive capacity neither in the patients with SSc nor with control; in the patients with SSc, the expression of CTLA-4 in the surface of FrII and FrIII cells were decreased significantly (P<0.001,respectively), and CTLA-4 mRNA expression in FrII were decreased.

(4) The expression of IL-17 were higher in FrIII cells than FrI and FrII cells in both groups (P<0.001,respectively),but there were no difference of FrIII between these two groups; Th17 cells were increased in the patients with SSc (P<0.001); in the patients with SSc, CD25⁺FoxP₃⁺IL17⁺cells among CD4⁺cells were increased(0.075±0.032 vs 0.049±0.027, P=0.029),but no difference of  CD25⁺FoxP3⁺IL17^–with control; the expression of IL-17A and RORC mRNA were increased in the FrIII cells of SSc patients(P<0.001,respectively).

Conclusion:

Decreased aTreg with functional deficiency and increased CD45RA^–FoxP₃^lo T cells could explain increased Treg with dysfunction in the patients with SSc, which were the reasons of unbalance of Treg and Th17 cells in the patients with SSc too. Increased Treg cells were not the real regulatory T cells, but non-suppressive CD45RA^–FoxP₃^lo cells, which is the main provider for FoxP₃⁺IL-17⁺ cells without immunosuppressive capacity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/increase-of-cd4cd25foxp3-t-cell-in-patients-with-systemic-sclerosis-could-secret-il-17-with-dysfunction-of-immunosuppression/