Objective. To study the expression levels and immunostimulatory capacities of interleukin-7 (IL-7) in primary Sjögren's syndrome.Methods. Labial salivary gland (LSG) IL-7 expression was determined by immunohistochemistry, using a quantitative scoring system, in 30 patients with sicca syndrome: 15 patients with primary Sjögren's syndrome (SS) and 15 patients with non-SS sicca syndrome. The correlation of IL-7 expression in LSGs with parameters of local and peripheral disease was studied, and serum and salivary IL-7 levels were determined. Additionally, the effects of IL-7 on cytokine production by peripheral blood mononuclear cells (PBMCs) from patients with primary SS were determined in vitro by Luminex multicytokine assay and compared with the effects in control subjects.Results. The expression of IL-7 in LSGs was higher in patients with primary SS compared with that in patients with non-SS sicca syndrome. IL-7 was observed primarily in the vicinity of lymphocytic infiltrates. Salivary IL-7 levels in patients with primary SS were higher than those in control subjects. In all 30 patients with sicca syndrome, IL-7 expression in LSGs correlated with parameters of both local and peripheral disease. Furthermore, IL-7 stimulated T cell-attracting and T cell-differentiating cytokines (monokine induced by interferon-␥ [IFN␥], IFN␥-inducible 10-kd protein,
Post-traumatic stress disorder (PTSD) is associated with a dysregulation of the hypothalamus-pituitary-adrenal axis (HPA axis). In addition, there is evidence for altered glucocorticoid receptor (GR) expression and function in peripheral blood mononuclear cells. The aim of the present study was to differentiate between the effect of trauma exposure and PTSD on leukocyte GR expression and glucocorticoid immune regulation. Leukocyte GR binding characteristics and glucocorticoid sensitivity of immune activity, determined as the effect of dexamethasone (DEX) on in vitro cytokine release and T-cell proliferation, were compared between veterans with PTSD, traumatized veterans without PTSD and healthy controls. Leukocyte GR density was significantly lower in veterans with and without PTSD compared to healthy controls. DEX-induced inhibition of T-cell proliferation was significantly lower in PTSD compared to trauma and healthy controls. DEX-induced increase in lipopolysaccharidestimulated interleukin-10 was less pronounced in traumatized veterans with and without PTSD compared to healthy controls. No group differences were observed in the effect of DEX on other cytokines or in baseline immune activity, except for lower tumor necrosis factor-a production in PTSD patients compared to healthy controls. The results suggest that trauma exposure is sufficient to induce changes in GR binding characteristics, whereas resistance of T-cell proliferation to DEX only occurs in PTSD. DEX resistance of in vitro immune activity was not a general phenomenon, but was restricted to specific immune functions.
IL-7, expressed by stromal cells in primary lymphoid organs, is known for its critical role in the development and homeostatic expansion of T cells in humans and mice. IL-7 is equally important for B cell development in human and mice, but only in mice seems critical for B cell development and expansion. Recent studies demonstrate that this potent immunostimulatory cytokine is overexpressed in inflamed tissues of patients with (rheumatic) autoimmune diseases and that expression levels correlate with clinical parameters of disease. In inflamed tissues several cell types, including macrophages, dendritic cells, and fibroblasts produce IL-7. IL-7 primarily acts on T cells that abundantly express the IL-7 receptor and that are increased at the inflammatory sites, and predominantly induces Th1 and Th17-associated cytokine secretion. IL-7-mediated T cell-dependent activation of macrophages, dendritic cells and B cells is accompanied by up regulation of T cell differentiating factors, chemokines, adhesion/co-stimulatory molecules and catabolic cytokines and enzymes. Moreover, overexpression of IL-7 is associated with ectopic lymphoid aggregate formation, corresponding with the capacity of IL-7 to induce LTβ and TNFα and to activate innate lymphoid tissue inducer cells. Additionally, IL-7 promotes T cell-driven osteoclastogenesis and fibroblast activation, processes involved in tissue destruction in chronic inflammation. Altogether this suggests that IL-7 is an important proinflammatory mediator in several chronic (rheumatic) inflammatory autoimmune diseases. The substantial amelioration of inflammation and immunopathology in experimental animal models for these diseases by blocking IL-7(receptor) supports this role of IL-7 and demonstrates that IL-7 and its receptor represent novel targets for immunotherapy.
IL-7Rα+ cells are highly proliferating cells that respond strongly to IL-7 despite an increased number of IL-7Rα- T cells that express FoxP3 and CD25. The recent finding that IL-7 and IL-7Rα+ T cells were both found to be increased in exocrine glands of pSS patients indicates that IL-7 could contribute to glandular inflammation by activation of IL-7Rα+ responder T cells despite the increased numbers of Tregs.
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