Lipopolysaccharide-induced suppression of airway Th2 responses does not require IL-12 production by dendritic cells

The prevalence of atopic asthma, a Th2-dependent disease, is reaching epidemic proportions partly due to improved hygiene in industrialized countries. There is an inverse correlation between the level of environmental endotoxin exposure and the prevalence of atopic sensitization. As dendritic cells (DC) have been implicated in causing sensitization to inhaled Ag, we studied the effect of endotoxin on Th2 development induced by bone marrow DC in vitro and by intratracheal injection in vivo, with particular emphasis on the role played by the polarizing cytokine IL-12. Bone marrow-derived DC stimulated with Escherichia coli O26:B6 LPS produced IL-12p70 for a limited period of time, after which production became refractory to further stimulation with CD40 ligand, a phenomenon previously called "exhaustion." The level of IL-12 production of DC did not correlate with Th1 development, as exhausted OVA-pulsed DC were still capable of shifting the cytokine pattern of responding OVA-specific Th cells toward Th1 in vitro and in vivo. When mice were first immunized by intratracheal injection of OVA-DC and subsequently challenged with OVA aerosol, prior in vitro stimulation of DC with LPS reduced the development of airway eosinophilia and Th2 cytokine production. Most surprisingly, the capacity of LPS to reduce Th2-dependent eosinophilic airway inflammation was IL-12-independent altogether, as IL-12p40 knockout DC had a similar reduced capacity to prime for Th2 responses. These results suggest that LPS reduces sensitization to inhaled Ag by reducing DC-driven Th2 development, but that IL-12 is not necessary for this effect.     

IL-10-dependent suppression of experimental allergic encephalomyelitis by Th2-differentiated, anti-TCR redirected T lymphocytes

We previously showed that transgenically expressed chimeric Ag-MHC-zeta receptors can Ag-specifically redirect T cells against other T cells. When the receptor's extracellular Ag-MHC domain engages cognate TCR on an Ag-specific T cell, its cytoplasmic zeta-chain stimulates the chimeric receptor-modified T cell (RMTC). This induces effector functions such as cytolysis and cytokine release. RMTC expressing a myelin basic protein (MBP) 89-101-IAs-zeta receptor can be used therapeutically, Ag-specifically treating murine experimental allergic encephalomyelitis (EAE) mediated by MBP89-101-specific T cells. In initial studies, isolated CD8+ RMTC were therapeutically effective whereas CD4+ RMTC were not. We re-examine here the therapeutic potential of CD4+ RMTC. We demonstrate that Th2-differentiated, though not Th1-differentiated, CD4+ MBP89-101-IAs-zeta RMTC prevent actively induced or adoptively transferred EAE, and treat EAE even after antigenic diversification of the pathologic T cell response. The Th2 RMTC both Th2-deviate autoreactive T cells and suppress autoantigen-specific T cell proliferation. IL-10 is critical for the suppressive effects. Anti-IL-10R blocks RMTC-mediated modulation of EAE and suppression of autoantigen proliferation, as well as the induction of IL-10 production by autoreactive T cells. In contrast to IL-10, IL-4 is required for IL-4 production by, and hence Th2 deviation of autoreactive T cells, but not the therapeutic activity of the RMTC. These results therefore demonstrate a novel immunotherapeutic approach for the Ag-specific treatment of autoimmune disease with RMTC. They further identify an essential role for IL-10, rather than Th2-deviation itself, in the therapeutic effectiveness of these redirected Th2 T cells.     

Induction of a Th1 response from Th2-polarized T cells by activated dendritic cells: dependence on TCR:peptide-MHC interaction, ICAM-1, IL-12, and IFN-gamma

Dendritic cells (DC) are important regulators of T cell immunity. The degree of stimulation, the pattern of costimulatory molecules expressed, and the cytokines secreted by DC dictate the nature of the effector and memory cells generated, particularly with respect to their Th1 or Th2 phenotypes. In this study, we demonstrate that the addition of activated DC to spleen cultures containing established Th2-polarized CD4(+) T cells was sufficient to suppress Th2 and induce Th1 cytokines in a recall response, a phenomenon referred to as phenotype reversal. The ability of activated DC to induce phenotype reversal displayed exquisite Ag specificity. The DC activator B7-DC cross-linking Ab (XAb) was >10,000-fold more efficient at inducing phenotype reversal than the TLR agonists CpG-oligodeoxynucleotide and Gardiquimod. Characterization of the mechanisms governing phenotype reversal revealed the requirement for cognate interaction between the TCR:peptide-MHC complex, the expression of the costimulation/adhesion molecule ICAM-1, and secretion of IL-12 and IFN-gamma by the activated DC. The requirement for the costimulation/adhesion molecule SLAM (signaling lymphocytic activation molecule) was found to be quantitative. Thus, activation of DC, particularly by crosslinking B7-DC, can modulate well-established Th2 T cell responses in an Ag-specific manner. Because the regulation of mouse and human DC by B7-DC XAb overlaps in several significant ways, immune modulation with B7-DC XAb is a potential strategy for treating Th2-mediated diseases.     

Leukotriene B4 receptor 1 expression on dendritic cells is required for the development of Th2 responses and allergen-induced airway hyperresponsiveness

Dendritic cells (DC) are important APCs that control allergen-induced airway responses by interacting directly with T cells. Leukotriene B(4) (LTB(4)), interacting with its high-affinity receptor, LTB(4) receptor 1 (BLT1), is known to attract and activate leukocytes during inflammation. We have previously shown that BLT1 expression on Ag-primed T cells is required for the development of airway hyperresponsiveness (AHR; Miyahara et al. 2005. Am. J. Respir. Crit. Care Med. 172: 161-167). However, the role for the LTB(4)-BLT1 pathway in DC function in allergen-induced airway responses has not been defined. Bone marrow-derived DCs (BMDC) were generated. Naive BALB/c mice received OVA-pulsed BLT1-deficient (BLT1(-/-)) BMDCs or wild-type BMDCs intratracheally and were then challenged with OVA for 3 days. Airway responses were monitored 48 h after the last allergen challenge. BLT1(-/-) BMDCs showed normal maturation judged from surface expression of CD markers. Compared with recipients of wild-type BMDCs, mice that received BLT1(-/-) BMDCs developed significantly lower AHR to inhaled methacholine, lower goblet cell metaplasia, and eosinophilic infiltration in the airways and decreased levels of Th2 type cytokines in the bronchoalveolar lavage fluid. Migration of BLT1(-/-) BMDCs into peribronchial lymph nodes was significantly impaired compared with BLT1(+/+) BMDCs after intratracheal instillation. These data suggest that BLT1 expression on DCs is required for migration of DCs to regional lymph nodes as well as in the development of AHR and airway inflammation.     

GITR signaling potentiates airway hyperresponsiveness by enhancing Th2 cell activity in a mouse model of asthma

Background

Anxiety and depression are common and treatable risk factors for re-hospitalisation and death in patients with COPD. The degree of lung function impairment does not sufficiently explain anxiety and depression. The BODE index allows a functional classification of COPD beyond FEV₁. The aim of this cross-sectional study was (1) to test whether the BODE index is superior to the GOLD classification for explaining anxious and depressive symptoms; and (2) to assess which components of the BODE index are associated with these psychological aspects of COPD.

Methods

COPD was classified according to the GOLD stages based on FEV_1%predicted in 122 stable patients with COPD. An additional four stage classification was constructed based on the quartiles of the BODE index. The hospital anxiety and depression scale was used to assess anxious and depressive symptoms.

Results

The overall prevalence of anxious and depressive symptoms was 49% and 52%, respectively. The prevalence of anxious symptoms increased with increasing BODE stages but not with increasing GOLD stages. The prevalence of depressive symptoms increased with both increasing GOLD and BODE stages. The BODE index was superior to FEV_1%predicted for explaining anxious and depressive symptoms. Anxious symptoms were explained by dyspnoea. Depressive symptoms were explained by both dyspnoea and reduced exercise capacity.

Conclusion

The BODE index is superior to the GOLD classification for explaining anxious and depressive symptoms in COPD patients. These psychological consequences of the disease may play a role in future classification systems of COPD.     

IL-4 is a mediator of IL-12p70 induction by human Th2 cells: reversal of polarized Th2 phenotype by dendritic cells

IL-12 is a key inducer of Th1-associated inflammatory responses, protective against intracellular infections and cancer, but also involved in autoimmune tissue destruction. We report that human Th2 cells interacting with monocyte-derived dendritic cells (DC) effectively induce bioactive IL-12p70 and revert to Th0/Th1 phenotype. In contrast, the interaction with B cells preserves polarized Th2 phenotype. The induction of IL-12p70 in Th2 cell-DC cocultures is prevented by IL-4-neutralizing mAb, indicating that IL-4 acts as a Th2 cell-specific cofactor of IL-12p70 induction. Like IFN-gamma, IL-4 strongly enhances the production of bioactive IL-12p70 heterodimer in CD40 ligand-stimulated DC and macrophages and synergizes with IFN-gamma at low concentrations of both cytokines. However, in contrast to IFN-gamma, IL-4 inhibits the CD40 ligand-induced production of inactive IL-12p40 and the production of either form of IL-12 induced by LPS, which may explain the view of IL-4 as an IL-12 inhibitor. The presently described ability of IL-4 to act as a cofactor of Th cell-mediated IL-12p70 induction may allow Th2 cells to support cell-mediated immunity in chronic inflammatory states, including cancer, autoimmunity, and atopic dermatitis.     

Cytokine production by dendritic cells genetically engineered to express IL-4: induction of Th2 responses and differential regulation of IL-12 and IL-23 synthesis

Dendritic cells (DCs) retrovirally transduced with IL-4 have recently been shown to inhibit murine collagen-induced arthritis and associated Th1 immune responses in vivo, but the mechanisms that underly these effects are not yet understood. In this report we demonstrate that IL-4-transduced DCs loaded with antigen led to lower T cell production of IFN-gamma, increased production of IL-4, and an attenuated, delayed type hypersensitivity response. We hypothesized that the ability of such DCs to regulate the Th1 immune response in vivo depends in part on their capacity to produce IL-12 and IL-23. Quantitative mRNA analysis revealed that IL-4-transduced DCs stimulated with CD40 ligand expressed higher levels of IL-12p35 mRNA, but lower levels of mRNA for IL-23p19 and the common subunit p40 found in both IL-12 and IL-23, compared with control DCs. These results, which indicate that expression of the IL-12 and IL-23 subunits is differentially regulated in IL-4-transduced DCs, were confirmed by ELISA of the IL-12 and IL-23 heterodimers. Thus, therapeutic suppression of Th1 -mediated autoimmunity (as recently shown in murine collagen-induced arthritis) and induction of Th2 responses in vivo by IL-4-transduced DCs occurs despite their potential to produce increased levels of IL-12, but could reflect, in part, decreased production of IL-23.     

双歧杆菌对过敏性哮喘儿童树突状细胞分泌IL-10、IL-12等细胞因子的影响

目的探讨双歧杆菌对过敏性哮喘儿童外周血单核细胞（PBMC）来源的树突状细胞（DC）分泌IL-1β、IL-6、IL-10、IL-12、IL-23和IFN-γ的影响。方法从15例过敏性哮喘儿童和15例非哮喘儿童的外周血单个核细胞诱导生成未成熟DC,加入双歧杆菌后继续培养DC2d,用ELISA方法检测培养上清中IL-1β、IL-6、IL-10、IL-12、IL-23和IFN-γ的水平。结果双歧杆菌能明显刺激哮喘儿童DC分泌IL-12、IFN-γ,IL-1β及IL-6和非哮喘儿童DC分泌IL-12、IL-10、IL-1β及IL-23水平增高。结论双歧杆菌能够刺激过敏性哮喘儿童DC分泌IL-12和IFN-γ,可能改变Th2优势分化,纠正Th1／Th2失衡。同时双歧杆菌还能刺激哮喘儿童DC分泌IL-1p及IL-6增高,达到促进,Th17细胞分化的作用。     

Cutting edge: polarized Th cell response induction by transferred antigen-pulsed dendritic cells is dependent on IL-4 or IL-12 production by recipient cells

To assess the influence of dendritic cell (DC) production of polarizing cytokines on Th2 and Th1 development we transferred Ag-pulsed DC generated from wild-type, IL-4(-/-), or IL-12(-/-) mice into wild-type, IL-4(-/-), or IL-12(-/-) recipients. We found that DC IL-4 was not necessary for Th2 induction and that, surprisingly, DC IL-12 was not an absolute requirement for Th1 development. However, DC IL-12 production facilitated optimal Th1 response development. Critically, recipient ability to produce IL-4 or IL-12 was essential for either Th2 or Th1 development. These data help delineate the source and importance of IL-4 and IL-12 in the process of induction of polarized T cell responses by DC.     

CD8 alpha+, but not CD8 alpha-, dendritic cells tolerize Th2 responses via contact-dependent and -independent mechanisms, and reverse airway hyperresponsiveness, Th2, and eosinophil responses in a mouse model of asthma

Splenic CD8alpha+ dendritic cells reportedly tolerize T cell responses by inducing Fas ligand-mediated apoptosis, suppressing IL-2 expression, or catabolizing T cell tryptophan reserves through expression of IDO. We report in this study that CD8alpha+, but not CD8alpha-, dendritic cells purified from the spleens of normal mice can tolerize the Th2 responses of cells from asthma phenotype mice through more than one mechanism. This tolerance could largely be reversed in vitro by anti-IL-10 or anti-TGFbeta Ab treatment. However, loss of direct dendritic cell-T cell contact also reduced tolerance, although to a lesser extent, as did adding the IDO inhibitor 1-methyltryptophan or an excess of free tryptophan to the cultures. Within 3 wk of reconstituting asthma phenotype mice with 1 x 10(5) OVA-pulsed CD8alpha+, but not CD8alpha-, dendritic cells, the mice experienced a reversal of airway hyperresponsiveness, eosinophilic airway responses, and pulmonary Th2 cytokine expression. This data indicates that CD8alpha+ dendritic cells can simultaneously use multiple mechanisms for tolerization of T cells and that, in vivo, they are capable of tolerizing a well-established disease complex such as allergic lung disease/asthma.     

IL-6 and IL-10 induction from dendritic cells in response to Mycobacterium tuberculosis is predominantly dependent on TLR2-mediated recognition

The initial TLR-mediated interaction between Mycobacterium tuberculosis and dendritic cells is critical, since the cytokine production that ensues can greatly influence the class of adaptive immunity that is generated to the pathogen. In this study, we therefore determined the dependency on TLR2 and TLR4 for M. tuberculosis-induced cytokine production by murine dendritic cells. A key new finding of this study is that production of IL-6 and IL-10 from dendritic cells in response to M. tuberculosis is principally dependent on TLR2. The study also indicates that M. tuberculosis can induce IL-12 production in the absence of either TLR2 or TLR4, suggesting redundancy or possibly involvement of other receptors in IL-12 production. In addition, the data also reveal that lack of TLR2 or TLR4 does not impact on dendritic cell maturation or on their ability to influence the polarity of differentiating naive T cells. Collectively, data presented here provide a mechanistic insight for the contribution of TLR2 and TLR4 to tuberculosis disease progression and offer strategies for regulating IL-6 and IL-10 production in dendritic cell-based vaccine strategies.     

Cutting edge: Th2 response induction by dendritic cells: a role for CD40.

We investigated the influence of dendritic cell (DC) CD40 expression on Th2 and Th1 development by in vivo transfer of Ag-pulsed bone marrow-derived DC generated from wild-type (WT) or CD40(-/-) mice. Contrary to expectation, CD40(-/-) DC primed with Ag that inherently induce a Th2 response (soluble egg Ag from Schistosoma mansoni) failed to induce a Th2 response or any compensatory Th1 response, whereas CD40(-/-)DC primed with Ag that inherently induce a Th1 response (Propionibacterium acnes) generated a competent Th1 response. Thus, DC expression of CD40 is a prerequisite for initiation of Th2, but not Th1, responses by these Ag. Consistent with this, CD154(-/-) mice, unlike WT mice, failed to mount a Th2 response when directly injected with schistosome eggs but mounted a normal Th1 response after challenge with P. acnes. CD40-CD154 interaction can therefore play a major role in Th2 response induction.     

Induction of regulatory T cells and dominant tolerance by dendritic cells incapable of full activation

Transplants tolerated through a process known as infectious tolerance evoke continuous recruitment of regulatory T (Treg) cells that are necessary to maintain the unresponsive state. This state is maintained long-term and requires continuous Ag exposure. It is not known, however, whether infectious tolerance operates through sustained recruitment of pre-existing regulatory cells, induction of regulatory cells, or both. Using mice deficient in natural Treg cells, we show here that quiescent donor dendritic cells (DC) laden with histocompatibility Ag can induce Treg cells de novo that mediate transplantation tolerance. In contrast, fully activated DC fail to do so. These findings suggest that DC incapable of delivering full activation signals to naive T cells may favor their polarization toward a regulatory phenotype. Furthermore, they suggest a role for quiescent endogenous DC in the maintenance of the tolerant state.     

Th2 differentiation is unaffected by Jagged2 expression on dendritic cells

Expression of the Jagged Notch ligands by dendritic cells (DCs) has been suggested to play a role in instructing Th2 responses. Supporting this hypothesis, we found that Jagged2 but not Jagged1 expression, correlates with the ability of DCs to induce Th2 responses. Jagged2 expression is up-regulated in response to the helminth soluble Schistosoma mansoni egg Ag, which conditions DCs to induce Th2 responses, and is markedly down-regulated following exposure to TLR agonists that generally promote Th1 responses. Conversely, Jagged1 expression is markedly induced by TLR ligation. Despite these correlations, suppression of expression of Jagged2 using retrovirally delivered small interfering RNA failed to affect the ability of DCs to induce Th2 cell differentiation either in vitro or in vivo. Moreover, retrovirally induced expression of Jagged2 did not enhance the ability of DCs to induce Th2 cell responses. Our data indicate that Jagged2 expression by DCs is not sufficient or required for Th2 cell differentiation.     

Interleukin-26: an IL-10-related cytokine produced by Th17 cells

IL-26 is classified as a member of the IL-10 cytokine family because it has limited sequence homology to IL-10 and the IL-10-related cytokines. The human IL-26 gene, IL26, is located on chromosome 12q15 between the genes for two other important class-2 cytokines, IFNG (IFN-γ) and IL22 (IL-22). IL-26 is often co-expressed with IL-22 by activated T cells, especially Th17 cells. It signals through a heterodimeric receptor complex composed of the IL-20R1 and IL-10R2 chains. IL-26 receptors are primarily expressed on non-hematopoietic cell types, particularly epithelial cells. Signaling through IL-26 receptor complexes results in the activation of STAT1 and STAT3 with subsequent induction of IL-26-responsive genes. The biological functions of IL-26 have only begun to be defined.     

IL-10 reduces Th2 cytokine production and eosinophilia but augments airway reactivity in allergic mice

Mononuclear phagocytes can interact with mesenchymal cells and extracellular matrix components that are crucial for connective tissue rearrangement. We asked whether blood monocytes can alter matrix remodeling mediated by human lung fibroblasts cultured in a three-dimensional collagen gel. Blood monocytes from healthy donors (>95% pure) were cast into type I collagen gels that contained lung fibroblasts. Monocytes in coculture inhibited the fibroblast-mediated gel contractility in a time- and concentration-dependent manner. The concentration of PGE(2), a well-known inhibitor of gel contraction, was higher (P < 0.01) in media from coculture; this media attenuated fibroblast gel contraction, whereas conditioned media from either cell type cultured alone did not. Three-dimensional cultured monocytes responded to conditioned media from cocultures by producing interleukin-1beta and tumor necrosis factor-alpha, whereas fibroblasts increased synthesis of PGE(2). Antibodies to interleukin-1beta and tumor necrosis factor-alpha blocked the monocyte inhibitory effect and reduced the amount of PGE(2) produced. The ability of monocytes to block the fibroblast contraction of matrix may be an important mechanism in regulating tissue remodeling.     

Effects of Th2 cytokines on chemokine expression in the lung: IL-13 potently induces eotaxin expression by airway epithelial cells

Airway inflammation associated with asthma is characterized by massive infiltration of eosinophils, mediated in part by specific chemoattractant factors produced in the lung. Allergen-specific Th2 cells appear to play a central role in asthma; for example, adoptively transferred Th2 cells induced lung eosinophilia associated with induction of specific chemokines. Interestingly, Th2 supernatant alone administered intranasally to naive mice induced eotaxin, RANTES, monocyte-chemotactic protein-1, and KC expression along with lung eosinophilia. We tested the major cytokines individually and found that IL-4 and IL-5 induced higher levels of macrophage-inflammatory protein-1alpha and KC; IL-4 also increased the production of monocyte-chemotactic protein-1; IL-13 and IL-4 induced eotaxin. IL-13 was by far the most potent inducer of eotaxin; indeed, a neutralizing anti-IL-13 Ab removed most of the eotaxin-inducing activity from Th2 supernatants, although it did not entirely block the recruitment of eosinophils. While TNF-alpha did not stimulate eotaxin production by itself, it markedly augmented eotaxin induction by IL-13. IL-13 was able to induce eotaxin in the lung of JAK3-deficient mice, suggesting that JAK3 is not required for IL-13 signaling in airway epithelial cells; however, eosinophilia was not induced in this situation, suggesting that JAK3 transduces other IL-13-mediated mechanisms critical for eosinophil recruitment. Our study suggests that IL-13 is an important mediator in the pathogenesis of asthma and therefore a potential target for asthma therapy.