No abstract

Effector T‐cell responses can be modulated by competing positive or negative signals transduced by NK‐cell receptors (NKR). In the CD4+ T‐cell population, the expression of NKR is primarily found in the CD4+CD28− T‐cell subset, also known as CD28null T cells. These T cells are frequently found in rheumatoid arthritis (RA) and other inflammatory disorders, suggesting that signaling through NKR may play a role in the autoimmune reaction. Here we aimed to dissect the phenotype and function of NKR‐expressing CD4+CD28− T cells in patients with RA. By analyzing a broad array of NKR on CD4+CD28− T cells we found a significant expression of the co‐activating receptors 2B4 (CD244), DNAM‐1 (CD226), and CRACC. Pair‐wise ligations of 2B4 with DNAM‐1 and/or NKG2D lead to increased effector functions of primary CD4+CD28− T cells to suboptimal levels of anti‐CD3 stimulation. Using multi‐parameter flow cytometry, we demonstrate that such co‐ligation led to an increased magnitude in overall responsiveness without changing qualitative aspects of the response. Altogether these results demonstrate a pattern of additive effects in NKR‐mediated functional modulation of CD4+CD28− T cells in RA. This may have consequences for the inflammatory responses imposed by these cells, thus influencing disease manifestations.

BackgroundTransforming growth factor (TGF)-β is an important modulator of immune functions and cellular responses, such as differentiation, proliferation, migration and apoptosis. The Smad proteins, which are intracellular TGF-β signal transducers, mediate most actions of TGF-β.ObjectivesThis study examines the role of Smad3 in a murine model of contact hypersensitivity (CHS).MethodsThe CHS response to oxazolone was studied in Smad3-deficient mice. The ear swelling response was measured and skin biopsies from oxazolone-sensitized skin areas were obtained for RNA isolation, immunohistochemical analyses and histology. Ear draining lymph nodes were collected for RNA isolation and proliferation tests. Quantitative real-time polymerase chain reaction was used to quantify mRNA expression of cytokines, chemokines and transcription factors.ResultsThe expression of proinflammatory [interleukin (IL)-1β, tumour necrosis factor-α, IL-6], Th2 (IL-4) and Th17 type cytokines (IL-17), as well as regulatory components (TGF-β, Foxp3) increased significantly at the mRNA level in the skin of oxazolone-treated Smad3−/− mice when compared with wild-type controls. The expression of the Th1 type cytokine IFN-γ and the chemokines CXCL9 and CXCL10 was, however, unaffected by the lack of Smad3. The number of neutrophils and expression of the chemokines CCL3 and CXCL5, which are both involved in neutrophil recruitment, were increased in mice lacking Smad3. Also Th2 type chemokines CCL24, CCL3 and CXCL5 were increased in the skin of Smad3−/− mice compared with wild-type mice. In the lymph nodes, mRNA of IL-1β and IL-17, but not IL-4, TGF-β or Foxp3, was increased in Smad3−/− mice during the CHS response.ConclusionsThe lack of intact TGF-β signalling via Smad3 results in an increased proinflammatory, Th2 and Th17 type response in the skin, as well as increased expression of regulatory elements such as TGF-β and Foxp3. Understanding the role of Smad3 in the CHS response may offer treatment and prevention strategies in this often disabling disease.

This study investigates the role of Smad3 signalling for the T-helper2 (Th2) cytokine homeostasis in normal lungs and in a mouse model of asthma.We used mice deficient for Smad3, a central part of the major signal transduction pathway for TGF-β and other related cytokines, and a mouse model for allergic asthma with ovalbumin (OVA) as the antigen.Compared to wild type mice, naive (unmanipulated) Smad3-/- mice exhibited significantly increased levels of proinflammatory cytokines and IL-4 as well as the Th2 associated transcription factor GATA-3 in the lung tissue and bronchoalveolar lavage (BAL). In the asthma model, mucin secretion and airway hyperresponsiveness (AHR) after allergen exposure was significantly increased in the Smad3-/- mice as compared to wild type (WT) mice. IL-4 levels in Smad3-/- were similar to those encountered in WT mice but IL-13 levels were decreased in the airways of OVA sensitized Smad3-/- mice compared to corresponding WT mice.The results indicate that a lack of Smad3 dependent signalling in the normal state will lead to an increase in the GATA-3 levels and as a result of this the levels of IL-4 increase. However, the lack of Smad3 also seems to inhibit expression of some cytokines, especially IL-13. Our results also indicate that in the inflammatory state TGF-β or related cytokines functions to counterbalance the effects of IL-4 rather than to critically regulate its expression.