Dendritic cell co-transfected with FasL and allergen genes induces T cell tolerance and decreases airway inflammation in allergen induced murine model

Serum amyloid A inhibits dendritic cell apoptosis to induce glucocorticoid resistance in CD4(+) T cells

Mediators produced by the airway epithelium control the activation, recruitment, and survival of pulmonary dendritic cells (DC) that present antigen to CD4(+) T cells during the genesis and exacerbation of allergic asthma. The epithelial-derived acute phase protein, serum amyloid A (SAA), induces DC maturation and TH17 polarization. TH17 responses are associated with severe forms of allergic asthma that are poorly controlled by corticosteroids. We sought to determine whether SAA would enhance the survival of DC during serum starvation and could then contribute to the development of a glucocorticoid-resistant phenotype in CD4(+) T cells. Bone marrow-derived dendritic cells (BMDC) that were serum starved in the presence of SAA were protected from activation of caspase-3 and released less lactate dehydrogenase. In comparison with untreated serum-starved BMDC, treatment with SAA downregulated mRNA expression of the pro-apoptotic molecule Bim, increased production of the pro-survival heat shock protein 70 (HSP70), and induced secretion of pro-inflammatory cytokines. SAA-treated BMDC that were serum starved for 48 h remained capable of presenting antigen and induced OTII CD4(+) T cells to secrete IL-17A, IL-17F, IL-21, IL-22, and IFNγ in the presence of ovalbumin. IL-17A, IL-17F, IL-21, and IFNγ production occurred even when the CD4(+) T cells were treated with dexamethasone (Dex), whereas glucocorticoid treatment abolished cytokine secretion by T cells cocultured with untreated serum-starved BMDC. Measurement of Dex-responsive gene expression demonstrated CD4(+) T cells as the target of glucocorticoid hyperresponsiveness manifest as a consequence of BMDC stimulation by SAA. Finally, allergic airway disease induced by SAA and antigen inhalation was unresponsive to Dex treatment. Our results indicate that apo-SAA affects DC to both prolong their viability and increase their inflammatory potential under apoptosis-inducing conditions. These findings reveal mechanisms through which SAA enhances the CD4(+) T-cell-stimulating capacity of antigen-presenting cells that may actively participate in the pathogenicity of glucocorticoid-resistant lung disease.

Mechanisms of peripheral tolerance to allergens

The immune system is regulated to protect the host from exaggerated stimulatory signals establishing a state of tolerance in healthy individuals. The disequilibrium in immune regulatory vs effector mechanisms results in allergic or autoimmune disorders in genetically predisposed subjects under certain environmental conditions. As demonstrated in allergen-specific immunotherapy and in the healthy immune response to high-dose allergen exposure models in humans, T regulatory cells are essential in the suppression of Th2-mediated inflammation, maintenance of immune tolerance, induction of the two suppressive cytokines interleukin-10 and transforming growth factor-β, inhibition of allergen-specific IgE, and enhancement of IgG4 and IgA. Also, suppression of dendritic cells, mast cells, and eosinophils contributes to the construction of peripheral tolerance to allergens. This review focuses on mechanisms of peripheral tolerance to allergens with special emphasis on recent developments in the area of immune regulation.

Kinetic and distinct distribution of conventional dendritic cells in the early phase of lipopolysaccharide-induced acute lung injury

Respiratory dendritic cells (DCs), especially conventional DCs (cDCs), are critically involved in the induction phase of the immune response in the respiratory system. However, little information concerning cDC kinetics in acute lung injury (ALI) is available. In this study, we have used a murine model of LPS-induced ALI to examine the kinetics and phenotype of respiratory, circulating and splenic cDCs. cDCs in the lung, blood, and spleen and the IL-6 level in the lung were detected at 6, 12 and 24 h after PBS or LPS challenge. In the ALI group, a rapid cDCs accumulation in the lung was observed, and there were highly significant correlations between the frequency of respiratory cDCs or the percentage of cDC expressing CD80 and the IL-6 concentration. However, the frequency of peripheral blood cDCs decreased rapidly in ALI mice, followed by a marked expansion. In addition, splenic cDCs only showed a transient expansion in ALI. cDCs within the blood, lungs and spleens had undergone a modest maturation in the ALI group. Our findings demonstrate that LPS-induced ALI provokes a dynamic and distinct distribution as well as phenotype changes in pulmonary, circulatory and splenic cDC populations. Lung cDCs may participate in the early inflammatory response to ALI.

Tolerogenic dendritic cells as a target for the therapy of immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease in which platelets are destroyed by special antiplatelet autoantibodies produced by B cells. Dendritic cells (DCs) are professional antigen-presenting cells involved in humoral immunity and cellular immunity and among them DCs that induce autoimmune tolerance are called tolerogenic DCs (tDCs). As a promising immunotherapeutic strategy for ITP, tDCs have received increasing attention. In this review, we describe the significant role of DCs in regulating autoimmune balances, introduce the manipulation strategies to generate tDCs, summarize recent progress on the experimental application of tDCs for ITP therapy, and finally discuss the perspectives of tolerogenic vaccination for ITP treatment in the clinic.

Treatment of allergic asthma: modulation of Th2 cells and their responses

Atopic asthma is a chronic inflammatory pulmonary disease characterised by recurrent episodes of wheezy, laboured breathing with an underlying Th2 cell-mediated inflammatory response in the airways. It is currently treated and, more or less, controlled depending on severity, with bronchodilators e.g. long-acting beta agonists and long-acting muscarinic antagonists or anti-inflammatory drugs such as corticosteroids (inhaled or oral), leukotriene modifiers, theophyline and anti-IgE therapy. Unfortunately, none of these treatments are curative and some asthmatic patients do not respond to intense anti-inflammatory therapies. Additionally, the use of long-term oral steroids has many undesired side effects. For this reason, novel and more effective drugs are needed. In this review, we focus on the CD4+ Th2 cells and their products as targets for the development of new drugs to add to the current armamentarium as adjuncts or as potential stand-alone treatments for allergic asthma. We argue that in early disease, the reduction or elimination of allergen-specific Th2 cells will reduce the consequences of repeated allergic inflammatory responses such as lung remodelling without causing generalised immunosuppression.

Molecular cloning, expression, sequence analyses of dust mite allergen Der f 6 and its IgE-binding reactivity with mite allergic asthma patients in southeast China

We report the cloning and molecular characterization of a full-length cDNA encoding house dust mite allergen, Der f 6 from D. farinae isolated in China. The full-length Der f 6 cDNA was obtained with 840 nucleotides long. Nucleotide sequencing analyses showed a total of 36 mutations in five Der f 6 cDNA clones, corresponding to 23 incompatible amino acid residues. Recombinant Der f 6 (rDer f 6) protein was successfully expressed in and purified from E. coli BL21. Among 20 asthmatic patients, 45% was positive to rDer f 6 by ELISA. Bioinformatics analyses revealed that the mature Der f 6 was a hydrophobic and extracellular protein with chymotrypsin-like serine protease activity, its secondary structure was composed of alpha helix (7.69%), extended strand (34.62%), random coils (57.69%), and the similarity of Der f 6 to Blo t 6, Sui m 6, Der f 3 and Der f 9 was 64, 65, 35, and 38%, respectively.