KLRG1 impairs regulatory T-cell competitive fitness in the gut.

Immune homeostasis requires the tight, tissue-specific control of the different CD4+ Foxp3+ regulatory T (Treg) cell populations. The cadherin-binding inhibitory receptor killer cell lectin-like receptor G1 (KLRG1) is expressed by a subpopulation of Treg cells with GATA3+ effector phenotype. Although such Treg cells are important for the immune balance, especially in the gut, the role of KLRG1 in Treg cells has not been assessed. Using KLRG1 knockout mice, we found that KLRG1 deficiency does not affect Treg cell frequencies in spleen, mesenteric lymph nodes or intestine, or frequencies of GATA3+ Treg cells in the gut. KLRG1-deficient Treg cells were also protective in a T-cell transfer model of colitis. Hence, KLRG1 is not essential for the development or activity of the general Treg cell population. We then checked the effects of KLRG1 on Treg cell activation. In line with KLRG1's reported inhibitory activity, in vitro KLRG1 cross-linking dampened the Treg cell T-cell receptor response. Consistently, lack of KLRG1 on Treg cells conferred on them a competitive advantage in the gut, but not in lymphoid organs. Hence, although absence of KLRG1 is not enough to increase intestinal Treg cells in KLRG1 knockout mice, KLRG1 ligation reduces T-cell receptor signals and the competitive fitness of individual Treg cells in the intestine.

Tumour-associated changes in intestinal epithelial cells cause local accumulation of KLRG1+ GATA3+ regulatory T cells in mice.

CD4+ Foxp3+ regulatory T (Treg) cells include differentiated populations of effector Treg cells characterized by the expression of specific transcription factors. Tumours, including intestinal malignancies, often present with local accumulation of Treg cells that can prevent tumour clearance, but how tumour progression leads to Treg cell accumulation is incompletely understood. Here using genetically modified mouse models we show that ablation of E-cadherin, a process associated with epithelial to mesenchymal transition and tumour progression, promotes the accumulation of intestinal Treg cells by the specific accumulation of the KLRG1+ GATA3+ Treg subset. Epithelial E-cadherin ablation activates the ß-catenin pathway, and we find that increasing ß-catenin signals in intestinal epithelial cells also boosts Treg cell frequencies through local accumulation of KLRG1+ GATA3+ Treg cells. Both E-cadherin ablation and increased ß-catenin signals resulted in epithelial cells with higher levels of interleukin-33, a cytokine that preferentially expands KLRG1+ GATA3+ Treg cells. Tumours often present reduced E-cadherin expression and increased ß-catenin signalling and interleukin-33 production. Accordingly, Treg cell accumulation in intestinal tumours from APCmin/+ mice was exclusively due to the increase in KLRG1+ GATA3+ Treg cells. Our data identify a novel axis through which epithelial cells control local Treg cell subsets, which may be activated during intestinal tumorigenesis.

Symptoms of shrinking lung syndrome reveal systemic lupus erythematosus in a 12-year-old girl.

While pleuropulmonary involvement in systemic lupus erythematosus (SLE) is a common occurrence, shrinking lung syndrome (SLS) is a rare complication of SLE, particularly in children. We report on a teenager girl with a primary SLE diagnosis, which was based upon clinical, imaging, lung-function and histological findings ascertained to be compatible with SLS. Following a pneumonia, the patient developed inflammatory residues in the lower lobes, an event that probably caused diaphragmatic immobility and subsequently led to SLS. Treatment response to steroids, cyclophosphamide and hydroxychloroquine in this case was excellent, and efficacy was more profound than previously has been reported in the literature with respect to pediatric patients. This case report argues that prognosis of SLS in SLE is likely to be favorable when the diagnosis is made early and the disease is treated appropriately.

Small interfering RNA against transcription factor STAT6 inhibits allergic airway inflammation and hyperreactivity in mice.

In the context of allergic immune responses, activation of STAT6 is pivotal for Th2-mediated IgE production and development of airway inflammation and hyperreactivity. We analyzed whether gene silencing of STAT6 expression by RNA interference was able to suppress allergen-induced immune and airway responses. Knockdown effectiveness of three different STAT6 siRNA molecules was analyzed in murine and human cell cultures. The most potent siRNA was used for further testing in a murine model of allergen-induced airway inflammation and airway hyperreactivity (AHR). BALB/c mice were sensitized with OVA/alum twice i.p. (days 1 and 14), and challenged via the airways with allergen (days 28-30). Intranasal application of STAT6 siRNA before and during airway allergen challenges reduced levels of infiltrating cells, especially of eosinophils, in the bronchoalveolar lavage fluid, compared with GFP siRNA-treated sensitized and challenged controls. Allergen-induced alterations in lung tissues (goblet cell hyperplasia, peribronchial inflammation with eosinophils and CD4 T cells) were significantly reduced after STAT6 siRNA treatment. Associated with decreased inflammation was a significant inhibition of the development of allergen-induced in vivo AHR after STAT6 siRNA treatment, compared with GFP siRNA-treated sensitized and challenged controls. Importantly, mRNA and protein expression levels of IL-4 and IL-13 in lung tissues of STAT6-siRNA treated mice were significantly diminished compared with sensitized and challenged controls. These data show that targeting the key transcription factor STAT6 by siRNA effectively blocks the development of cardinal features of allergic airway disease, like allergen-induced airway inflammation and AHR. It may thus be considered as putative approach for treatment of allergic airway diseases such as asthma.

Targeting allergic airway diseases by siRNA: an option for the future?

Allergic diseases emerge as a substantial health problem of the 21(st) century. Current therapies including combination therapies of corticosteroids and beta(2)-agonists are highly effective, inexpensive and relatively safe. However, these medicaments only relieve symptoms but are not curing disease. So the challenge has to be to develop new therapeutics which are as effective as present medicaments without any side effects and hopefully even heal the disease. It has become clear over the past years that Th2-cells and their cytokines have an outstanding role in the development of airway hyperresponsiveness, airway inflammation, airway remodelling and reversible airway obstruction, the cardinal symptoms of allergic asthma. There is legitimate hope that down regulation of these factors could result in a susceptible damage of pathologic mechanisms. Out of different gene silencing techniques RNAi seems to be the most promising method to achieve long-lasting and effective abrogation of key elements in allergic diseases. In particular, this review will highlight the potential of small interfering RNAs to specifically inhibit the function of transcription factors and tyrosine kinases which are involved in orchestrating an allergic immune response.