The Clinical Relevance of IL-17-Producing CD4+CD161+ Cell and Its Subpopulations in Primary Sjögren's Syndrome

Abstract

Objective: Th17 cells have been demonstrated to play an important role in the onset and development of primary Sjögren's syndrome (pSS). In this study, we evaluated the expansion and clinical significance of circulating CD4+CD161+ T cell and its "effector" (CD4+CD25-CD161+ T cell) and "regulatory" (CD4+CD25+CD161+ T cell) subpopulations.

Methods: Fifty-eight pSS patients and 16 healthy controls (HCs) were recruited in our study. The cell populations and intracellular IL-17 expression were analyzed by flow cytometry. The disease activity was evaluated by the EULAR-SS Disease Activity Index (ESSDAI). Autoantibodies were measured by ELISA or indirect immunofluorescence assay.

Results: The CD161+ T cell fractions showed higher proportions of IL-17-producing cells. The frequencies of the overall CD4+CD161+ T cell population and its effector subset were positively correlated with disease activity parameters and more severe disease manifestations. A significant elevation of the CD4+CD25+CD161+ T cell subpopulation was observed in the peripheral blood of pSS patients compared to HCs and this subset showed decreased regulatory functions compared with the CD4+CD25+CD161- population.

Conclusion: Circulating CD4+CD161+ T cell populations associated with pSS disease activity and severity. These cells might be involved in the development of pSS and could be potential therapeutic targets in the treatment of pSS.

Figure 1

IL-17 and IFN-γ production of the CD4+CD161+ T cell subsets in pSS. Representative flow cytometric plots of intracellular IL-17 or IFN-γ production in CD161+ or CD161− fraction of different T cell subsets were shown. Percentages of IL-17-producing or IFN-γ-producing cells in CD161+ and CD161− fractions in pSS patients (n = 6) were compared by paired t-test. ^∗ p < 0.05, ^∗∗ p < 0.01.

Figure 2

Most CD4+CD161+ T cells are CD45RO+. Representative flow cytometric plots of CD45RO expression on CD161+ or CD161− fraction of CD4+ T cell subset were shown. Percentages of CD4+CD45RO+ T cells in CD161+ and CD161− fractions in pSS patients (n = 6) were compared by paired t-test. ^∗∗ p < 0.01.

Figure 3

FACS analysis of circulating CD4+CD161+ T cell subsets. Representative data of CD4+CD25+CD161+ T (a), CD4+CD25−CD161+ T (b), and CD4+CD161+ T (c) from peripheral blood of patients with pSS (n = 58) and HCs (n = 16) were shown and percentages of circulating CD4+CD25+CD161+ T in CD4+CD25+ T (d), CD4+CD25−CD161+ T in CD4+CD25− T (e), and CD4+CD161+ T in CD4+ T (f) in pSS patients and HCs were compared by Mann-Whitney U test. ^∗∗∗ p < 0.0001.

Figure 4

Correlations of circulating CD4+CD161+ T cell subsets in pSS with laboratory values. CD4+CD161+ T cells were positively correlated with ESR (a) or platelet reduction (b). CD4+CD25−CD161+ T cells were positively correlated with ESR (c).

Figure 5

Percentages of CD4+CD161+ T (a to e) and CD4+CD25−CD161+ T (f to i) cells according to the disease features. ANA: antinuclear antibody; ESR: erythrocyte sedimentation rate; ESSDAI: the EULAR-SS Disease Activity Index. ^∗ p < 0.05.

Figure 6

Foxp3 and Helios expression of the CD4+CD25+CD161+ T cell subsets in pSS. Representative flow cytometric plots of transcription factor production in CD161+ or CD161− fraction of different T cell subsets were shown. Percentages of Foxp3-producing or Helios-producing cells in CD161+ and CD161− fractions in pSS patients (n = 6) were compared by paired t-test. ^∗ p < 0.05.

Figure 7

Compared with CD4+CD25−CD161+ T cells, the CD4+CD25+CD161+ T subset from peripheral blood of pSS patients showed impaired suppression activity on CD4+CD25− Teff from HC. (a) Unstimulated control; (b) CD4+CD25+CD161− T and Teff; (c) CD4+CD25+CD161+ T and Teff; (d) CD4+CD25− T and Teff. This result was representative of three independent experiments.