Maturation Of Lung Dendritic Cells Research Articles

Anti-CD1d treatment suppresses immunogenic maturation of lung dendritic cells dependent on lung invariant natural killer T cells in asthmatic mice

Our previous findings show that invariant natural killer T (iNKT)cells can promote immunogenic maturation of lung dendritic cells (LDCs) to enhance Th2 cell responses in asthma. It has been accepted that recognition of glycolipid antigens presented by CD1d molecules by the T cell receptors of iNKT cells leads to iNKT cell activation. Therefore, we examine the immunoregulatory influences of anti-CD1d treatment on Th2 cell response and immunogenic maturation of LDCs and subsequently explored whether these influences were dependent on lung iNKT cells in asthmatic mice. We discoveredthat in wild-type mice sensitized and challenged with house dust mite or ovalbumin (OVA), anti-CD1d treatment inhibited Th2 cell response and immunogenic maturation of LDCs. LDCs from asthmatic mice with anti-CD1d treatment had a markedly decreased influence on Th2 cell responses in vivo and in vitro. Furthermore, anti-CD1d treatment reduced the abundance and activation of lung iNKT cells in asthmatic mice. Moreover, in asthmatic iNKT cell-deficient Jα18-/- mice, anti-CD1d treatment did not influence Th2 cell responses and immunogenic maturation of LDCs. Meanwhile, the quantity of CD40L+ iNKT cells in asthmatic mice was significant decreased by anti-CD1d treatment. Finally, the inhibition of anti-CD1d treatment on LDC immunogenic maturation and Th2 cell responses in asthmatic mice was reversed by anti-CD40 treatment. Our data suggest that anti-CD1d treatment can suppress Th2 cell responses through inhibiting immunogenic maturation of LDCs dependent on lung iNKT cells, which couldbe partially related to the downregulation of CD40L expression on lung iNKT cells in asthmatic mice.

Blockade of CD40L inhibits immunogenic maturation of lung dendritic cells: Implications for the role of lung iNKT cells in mouse models of asthma

Some studies have shown that maturation of dendritic cells (DCs) is modulated directly by pathogen components via pattern recognition receptors such as Toll-like receptors, but also by signal like CD40 ligand (CD40 L or CD154) mediated by activated T cells. Several reports indicate that invariant natural killer T (iNKT) cells up-regulate CD40 L upon stimulation and thereby induce activation and maturation of DCs through crosslink with CD40. Our previous findings indicated that iNKT cells promote Th2 cell responses through the induction of immunogenic maturation of lung DCs (LDCs) in the asthmatic murine, but its mechanism remains unclear. Therefore, we investigated the immunomodulatory effects of blockade of CD40 L using anti-CD40 L treatment on Th2 cell responses and immunogenic maturation of LDCs, and further analyzed whether these influences of blockade of CD40 L were related to lung iNKT cells using iNKT cell-deficient mice and the combination treatment of specific iNKT cell activation with anti-CD40 L treatment in murine models of asthma. Our findings showed that blockade of CD40 L using anti-CD40 L treatment attenuated Th2 cell responses in wild-type (WT) mice, but not in CD1d-deficient mice sensitized and challenged with ovalbumin (OVA) or house dust mite (HDM). Meanwhile, blockade of CD40 L down-regulated immunogenic maturation of LDCs in WT mice, but not in CD1d-deficient mice sensitized and challenged with OVA. Additionally, agonistic anti-CD40 treatment reversed the inhibitory effects of anti-CD40 L treatment on Th2 cell responses and LDC activation in an OVA-induced mouse model of asthma. Furthermore, LDCs from asthmatic mice treated with anti-CD40 L could significantly reduce the influence on Th2 cell responses in vivo and in vitro. Finally, α-Galactosylceramide plus anti-CD40 L treatment stimulated lung iNKT cells, but suppressed Th2 cell responses in the asthmatic mice. Taken together, our data raise an evidence that blockade of CD40 L attenuates Th2 cell responses through the inhibition of immunogenic maturation of LDCs, which may be at least partially related to lung iNKT cells in murine models of asthma.

Sulfatide-activated type II NKT cells suppress immunogenic maturation of lung dendritic cells in murine models of asthma.

Our previous study showed that sulfatide-activated type II natural killer T (NKT) cells can prevent allergic airway inflammation in an ovalbumin (OVA)-induced murine model of asthma, but the underlying mechanism is unclear. Recently, sulfatide-activated type II NKT cells were shown to modulate the function of dendritic cells in experimental autoimmune encephalomyelitis and nonobese diabetic mice. Thus, it was hypothesized that sulfatide-activated type II NKT cells may modulate the function of lung dendritic cells (LDCs) in asthmatic mice. Our data showed that, in our mouse models, activation of type II NKT cells by sulfatide administration and adoptive transfer of sulfatide-activated type II NKT cells resulted in reduced expression of surface maturation markers and proinflammatory cytokine production of LDCs. LDCs from sulfatide-treated asthmatic mice, in contrast to LDCs from PBS-treated asthmatic mice, significantly reduced allergic airway inflammation in vivo. However, we found no influence of sulfatide-activated type II NKT cells on the phenotypic and functional maturation of bone marrow-derived dendritic cells in vitro. In addition, adoptive transfer of sulfatide-activated type II NKT cells did not influence the phenotypic and functional maturation of LDCs in CD1d-/- mice, which lack both type I and II NKT cells, immunized and challenged with OVA. Our data reveal that sulfatide-activated type II NKT cells can suppress immunogenic maturation of LDCs to reduce allergic airway inflammation in mouse models of asthma, and it is possible that the immunomodulatory effect needs type I NKT cells.

α-Galactosylceramide treatment before allergen sensitization promotes iNKT cell–mediated induction of Treg cells, preventing Th2 cell responses in murine asthma

Asthma is a common inflammatory pulmonary disorder involving a diverse array of immune cells such as proinflammatory T helper 2 (Th2) cells. We recently reported that intraperitoneal injection of α-galactosylceramide (α-GalCer) can stimulate the lung invariant natural killer T (iNKT) cells and does not lead to airway inflammation in WT mice. Other studies indicate that iNKT cells play an important role in inducing regulatory T cells (Treg cells) and peripheral tolerance. Using iNKT cell- knockout mice, functional inactivation of Treg cells, and co-culture experiments in murine asthma models, we investigated the immunoregulatory effects of α-GalCer treatment before allergen sensitization on Th2 cell responses. We also studied whether α-GalCer's effects require lung Treg cells induced by activated iNKT cells. Our results disclosed that intraperitoneal administration of α-GalCer before allergen sensitization could promote the expansion and suppressive activity of lung CD4+FoxP3+ Treg cells. These effects were accompanied by down-regulated Th2 cell responses and decreased immunogenic maturation of lung dendritic cells in WT mice. However, these changes were absent in CD1d-/- mice immunized and challenged with ovalbumin or house dust mites, indicating that the effects of α-GalCer on Treg cells mainly require iNKT cells. Moreover, functional inactivation of Treg cells could reverse the inhibitory ability of this α-GalCer therapy on Th2 cell responses in a murine asthma model. Our findings indicate that intraperitoneal administration of α-GalCer before the development of asthma symptoms induces the generation of lung Treg cells via iNKT cells and may provide a potential therapeutic strategy to prevent allergic asthma.

Invariant natural killer T cells promote immunogenic maturation of lung dendritic cells in mouse models of asthma.

Our previous study showed that invariant natural killer T (iNKT) cells might act as an adjuvant to promote Th2 inflammatory responses in an OVA-induced mouse model of allergic asthma, but the mechanism remains unknown. To clarify the underlying mechanism through which iNKT cells promote Th2 inflammatory responses, we investigated the modulatory influence of iNKT cells on phenotypic and functional maturation of lung dendritic cells (LDCs) using iNKT cell-knockout mice, specific iNKT cell activation, coculture experiments, and adoptive transfer of iNKT cells in mouse models of asthma. Our data showed that iNKT cell deficiency could downregulate surface maturation markers and proinflammatory cytokine secretion of LDCs from a mouse model of asthma. However, elevated activation of iNKT cells by α-galactosylceramide and adoptive transfer of iNKT cells could upregulate surface maturation markers and proinflammatory cytokine secretion of LDCs from mouse models of asthma. Meanwhile, iNKT cells significantly influenced the function of LDCs, markedly enhancing Th2 responses in vivo and in vitro. In addition, iNKT cell can induce LDCs expression of CD206 and RELM-α, reflecting alternative activation of LDCs in a mouse model of asthma. α-Galactosylceramide treatment significantly enhanced expression of CD40L of lung iNKT cells from a mouse model of asthma, and the coculture experiment of LDCs with iNKT cells showed that the blockade of CD40L strongly suppressed surface maturation markers and proinflammatory cytokine production by LDCs. Our data suggest that iNKT cells can promote immunogenic maturation of LDCs to enhance Th2 responses in mouse models of asthma.

Pulmonary alveolar macrophages contribute to the premetastatic niche by suppressing antitumor T cell responses in the lungs.

In contrast to tumor-associated macrophages, myeloid-derived suppressor cells, or inflammatory monocytes, functions of tissue resident macrophages, including alveolar macrophages (AM), in cancer were not well studied. Using a mouse model of breast cancer, we show that AM promote cancer metastasis to the lungs by suppressing antitumor T cells in this organ. AM accumulated in the premetastatic lungs through complement C5a receptor-mediated proliferation but not through recruitment from the circulation. AM preconditioned by breast tumors inhibited Th1 and favored generation of Th2 cells that had lower tumoricidal activity than Th1 cells. In addition, AM reduced the number and maturation of lung dendritic cells by regulating TGF-β in the lung environment. Depletion of AM reversed immunosuppression imposed by these cells and strengthened local Th1 responses, which significantly reduced lung metastatic burden. C5a receptor deficiency, which also lessens myeloid-derived suppressor cells in the premetastatic niche, synergized with the depletion of AM in preventing metastasis, leading to protection of mice from lung metastases. This study identifies AM as a new component of the premetastatic niche, which is harnessed by tumors to impose immunosuppression, and as a new target for cancer immunotherapies to eliminate or reduce metastasis. Because the lungs are the most common target for hematogenous metastasis, this research offers a plausible explanation for susceptibility of the lungs to cancer metastasis.

Indirect Toll-like receptor 5-mediated activation of conventional dendritic cells promotes the mucosal adjuvant activity of flagellin in the respiratory tract

The Toll-like receptor 5 (TLR5) agonist flagellin is an effective adjuvant for vaccination. Recently, we demonstrated that the adaptive responses stimulated by intranasal administration of flagellin and antigen were linked to TLR5 signaling in the lung epithelium. The present study sought to identify the antigen presenting cells involved in this adjuvant activity. We first found that the lung dendritic cells captured antigen very efficiently in a process independent of TLR5. However, TLR5-mediated signaling specifically enhanced the maturation of lung dendritic cells. Afterward, the number of antigen-bound and activated conventional dendritic cells (both CD11b+ and CD103+) increased in the mediastinal lymph nodes in contrast to monocyte-derived dendritic cells. These data suggested that flagellin-activated lung conventional dendritic cells migrate to the draining lymph nodes. The lymph node dendritic cells, in particular CD11b+ cells, were essential for induction of CD4 T-cell response. Lastly, neutrophils and monocytes were recruited into the lungs by flagellin administration but did not contribute to the adjuvant activity. The functional activation of conventional dendritic cells was independent of direct TLR5 signaling, thereby supporting the contribution of maturation signals produced by flagellin-stimulated airway epithelium. In conclusion, our results demonstrated that indirect TLR5-dependent stimulation of airway conventional dendritic cells is essential to flagellin's mucosal adjuvant activity.

Distinct Roles of Vascular Endothelial Growth Factor Receptor-1– and Receptor-2–Mediated Signaling in T Cell Priming and Th17 Polarization to Lipopolysaccharide-Containing Allergens in the Lung

Vascular endothelial growth factor (VEGF) is a key mediator in the development of airway immune dysfunction to inhaled allergens. However, the exact role of its receptors-mediated signaling is controversial. In this study, we evaluated the role of VEGF receptor (VEGFR)-1- and VEGFR-2-mediated signaling in T cell priming and polarization in the context of inhalation of LPS-containing allergens. A murine asthma model of mixed Th1 and Th17 cell responses was generated using intranasal sensitization with LPS-containing allergens. Pharmacologic intervention was performed during sensitization. In vivo production of VEGF and Th1- and Th17-polarizing cytokines (IL-12p70 and IL-6, respectively) were upregulated by airway exposure to LPS. Pharmacological intervention with a VEGFR-2-neutralizing Ab (anti-Flk1 mAb) abolished the production of IL-6 (but not IL-12p70) and the subsequent development of allergen-specific Th17 cell response. On the other hand, blocking VEGFR-1 signaling with a VEGFR-1 antagonist (anti-Flt1 hexapeptide) did not affect the production of IL-12p70 and IL-6. However, blocking VEGFR-1 signaling resulted in T cell tolerance rather than priming, mainly by inhibiting the maturation of lung dendritic cells, and their migration into lung-draining lymph nodes. These results suggest that T cell priming to LPS-containing allergens depends on VEGFR-1-mediated signaling, and the subsequent Th17 polarization depends on VEGFR-2 signaling.

Glucocorticoids hamper the ex vivo maturation of lung dendritic cells from their low autofluorescent precursors in the human bronchoalveolar lavage: decreases in allostimulatory capacity and expression of CD80 and CD86.

Dendritic cells (DCs) were prepared from human bronchoalveolar lavage (BAL) cells. We previously reported that, in particular, the CD1a fraction of the low autofluorescent (LAF) cells contains the precursors for DCs: after overnight culture, 40% of the LAF cells change into functionally and phenotypically prototypic dendritic/veiled cells. There are, as yet, no data on the modulatory effects of glucocorticoids (GC) on the maturation and function of such DCs isolated from the human lung. Functional tests (allogeneic mixed lymphocyte reaction: allo-MLR) were therefore performed with CD1a+ LAF cells at different stimulator-to-T-cell ratios and after preincubation with different dexamethasone (DEX) concentrations. DEX caused suppression of the T-cell stimulatory capacity of CD1a+ LAF cells, which was dose-dependent, and more evident at the higher stimulator-to-T-cell ratios. Here, we also show that CD80 and CD86 are normally expressed at low levels on CD1a+ LAF cell-derived DCs compared to other DC populations. This low-level expression of costimulatory molecules is discussed here in relation to the previously reported low-level expression of CD80 (and CD86) on lung DCs in experimental animals. This appears to play a role in a predominant Th2 cell stimulating potential of DC from the lung environment. DEX exposure of CD1a+ LAF cells prevented the upregulation of even this low-level expression of CD80 and CD86. The veiled/dendritic morphology and the expression of other relevant cell surface markers and adhesion molecules was not affected by DEX exposure. It is concluded that DEX hampers the maturation of CD1a+ LAF cells into active lung DCs.