Altered T-cell and regulatory cell repertoire in patients with diffuse cutaneous systemic sclerosis

Objectives: The aim of this study was to evaluate a wide spectrum of peripheral immune-competent cell types, reflecting overall disturbances in immune homeostasis, characteristic of systemic sclerosis (SSc). We also assessed visceral organ involvement and evaluated the relationship between cell proportions and clinical symptoms of the disease. Methods: Twenty-one patients with diffuse cutaneous SSc (dcSSc) and 15 healthy individuals participated in the study. Peripheral blood lymphocyte subgroups were quantified by flow cytometry, soluble cytokines were assessed by enzyme-linked immunosorbent assay (ELISA), serum complement levels were measured by nephelometry, and autoantibodies were determined by indirect immunofluorescence staining and ELISA technique. Functional tests of regulatory T (Treg) cells were also carried out. Results: Patients with SSc had higher percentages of activated CD3+/HLA-DR+ T cells. Comparing naive vs. memory subsets of CD4+ and CD8+ T cells, a shift towards central memory phenotype was observed in SSc. Natural killer (NK) and T-helper (Th) 17 cell percentages were increased, while NKT, Th1, Treg type 1 (Tr1), and CD4+CD25+ Treg cell percentages were decreased in patients. Moreover, the suppressor activity of CD4+CD25+ Treg cells was lower in SSc. Negative correlations occurred between modified Rodnan skin score (MRSS) and Tr1 cell percentages and between complement levels and CD4+CD25+ Treg cells. We also found decreased interleukin (IL)-10 levels in SSc. Conclusions: Our data suggest that the increased Th17/CD4+CD25+ Treg ratio and the altered regulatory function of CD4+CD25+ Treg cells play an important role in the development of SSc. Moreover, our study reveals the potential role of the decreased profile of IL-10-producing Tr1 cells in the progression of disproportionate immune responses in SSc.