Cutting edge: inhaled antigen upregulates retinaldehyde dehydrogenase in lung CD103+ but not plasmacytoid dendritic cells to induce Foxp3 de novo in CD4+ T cells and promote airway tolerance.
ABSTRACT: Dendritic cell (DC)-T cell interactions that underlie inducible/adaptive regulatory T cell generation and airway tolerance are not well understood. In this study, we show that mice lacking CD11c(hi) lung DCs, but containing plasmacytoid DCs (pDCs), fail tolerization with inhaled Ag and cannot support Foxp3 induction in vivo in naive CD4(+) T cells. CD103(+) DCs from tolerized mice efficiently induced Foxp3 in cocultured naive CD4(+) T cells but pDCs and lung macrophages failed to do so. CD103(+) DCs, but not pDCs or lung macrophages, upregulated the expression of retinaldehyde dehydrogenase 2 (aldh1a2), which is key for the production of retinoic acid, a cofactor for TGF-? for Foxp3 induction. Batf3(-/-) mice, selectively lacking CD103(+) DCs, failed tolerization by inhaled Ag. Collectively, our data show that pulmonary tolerance is dependent on CD103(+) DCs, correlating with their ability to upregulate aldh1a2, which can promote Foxp3 expression in T cells.
Project description:Allergic asthma stems largely from the actions of T helper 2 (Th2) cells, but the pathways that initiate Th2 responses to inhaled allergens are not fully understood. In the lung, there are two major subsets of dendritic cells (DCs), displaying CD11b or CD103. We found that after taking up inhaled ovalbumin in vivo, purified CD103(+) DCs from the lung or lung-draining lymph nodes primed Th2 differentiation ex vivo. Th2 induction by CD103(+) DCs was also seen when cockroach or house dust mite allergens were used. In contrast, CD11b(hi) DCs primed Th1 differentiation. Moreover, mice lacking CD103(+) DCs displayed diminished Th2 priming to various inhaled allergens and did not develop asthma-like responses following subsequent allergen challenge. Low-level antigen presentation by CD103(+) DCs was necessary, but not sufficient for Th2 priming. Together, these findings show that CD103(+) DCs have a significant role in priming Th2 responses to inhaled allergens.
Project description:Retinoic acid (RA) produced by intestinal dendritic cells (DCs) imprints gut-homing specificity on lymphocytes and enhances Foxp3(+) regulatory T-cell differentiation. The expression of aldehyde dehydrogenase (ALDH) 1A in these DCs is essential for the RA production. However, it remains unclear how the steady-state ALDH1A expression is induced under specific pathogen-free (SPF) conditions. Here, we found that bone marrow-derived dendritic cells (BM-DCs) generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) expressed Aldh1a2, an isoform of Aldh1a, but that fms-related tyrosine kinase 3 ligand-generated BM-DCs did not. DCs from mesenteric lymph nodes (MLN) and Peyer's patches (PP) of normal SPF mice expressed ALDH1A2, but not the other known RA-producing enzymes. Employing a flow cytometric method, we detected ALDH activities in 10-30% of PP-DCs and MLN-DCs. They were CD11c(high)CD4(-/low)CD8alpha(intermediate)CD11b(-/low) F4/80(low/intermediate)CD45RB(low)CD86(high)MHC class II(high)B220(-)CD103(+). Equivalent levels of aldehyde dehydrogenase activity (ALDHact) and ALDH1A2 expression were induced synergistically by GM-CSF and IL-4 in splenic DCs in vitro. In BM-DCs, however, additional signals via Toll-like receptors or RA receptors were required for inducing the equivalent levels. The generated ALDH1A2(+) DCs triggered T cells to express gut-homing receptors or Foxp3. GM-CSF receptor-deficient or vitamin A-deficient mice exhibited marked reductions in the ALDHact in intestinal DCs and the T cell number in the intestinal lamina propria, whereas IL-4 receptor-mediated signals were dispensable. GM-CSF(+)CD11c(-)F4/80(+) cells existed constitutively in the intestinal tissues. The results suggest that GM-CSF and RA itself are pivotal among multiple microenvironment factors that enable intestinal DCs to produce RA.
Project description:Foxp3(+) regulatory T (T reg) cells play a key role in controlling immune pathological re actions. Many develop their regulatory activity in the thymus, but there is also evidence for development of Foxp3(+) T reg cells from naive precursors in the periphery. Recent studies have shown that transforming growth factor (TGF)-beta can promote T reg cell development in culture, but little is known about the cellular and molecular mechanisms that mediate this pathway under more physiological conditions. Here, we show that after antigen activation in the intestine, naive T cells acquire expression of Foxp3. Moreover, we identify a population of CD103(+) mesenteric lymph node dendritic cells (DCs) that induce the development of Foxp3(+) T reg cells. Importantly, promotion of T reg cell responses by CD103(+) DCs is dependent on TGF-beta and the dietary metabolite, retinoic acid (RA). These results newly identify RA as a cofactor in T reg cell generation, providing a mechanism via which functionally specialized gut-associated lymphoid tissue DCs can extend the repertoire of T reg cells focused on the intestine.
Project description:Regulatory T cells (Tregs) play a critical role in the maintenance of airway tolerance. We report that inhaled soluble Ag induces adaptive Foxp3(+) Tregs, as well as a regulatory population of CD4(+) T cells in the lungs and lung-draining lymph nodes that express latency-associated peptide (LAP) on their cell surface but do not express Foxp3. Blocking the cytokine IL-10 or TGF-? prevented the generation of LAP(+) Tregs and Foxp3(+) Tregs in vivo, and the LAP(+) Tregs could also be generated concomitantly with Foxp3(+) Tregs in vitro by culturing naive CD4(+) T cells with Ag and exogenous TGF-?. The LAP(+) Tregs strongly suppressed naive CD4(+) T cell proliferation, and transfer of sorted OVA-specific LAP(+) Tregs in vivo inhibited allergic eosinophilia and Th2 cytokine expression in the lung, either when present at the time of Th2 sensitization or when injected after Th2 cells were formed. Furthermore, inflammatory innate stimuli from house dust mite extract, nucleotide-binding oligomerization domain containing 2 ligand, and LPS, which are sufficient for blocking airway tolerance, strongly decreased the induction of LAP(+) Tregs. Taken together, we concluded that inducible Ag-specific LAP(+) Tregs can suppress asthmatic lung inflammation and constitute a mediator of airway tolerance together with Foxp3(+) Tregs.
Project description:Retinoic acid (RA)-producing CD103+ mature dendritic cells (DCs) in mesenteric lymph nodes (MLNs) play crucial roles in gut immunity. GM-CSF and RA contribute to the expression of the RA-producing enzyme ALDH1A2. However, additional signals appeared to be required for inducing ALDH1A2high mature DCs from immature DCs. We found here that TLR ligands (Ls) and immobilized E-cadherin could provide such signals in FLT3-L-generated bone marrow (BM)-derived DCs after treatment with GM-CSF and the RA receptor agonist Am80. The TLR-L-treated DCs produced proinflammatory cytokines unlike normal ALDH1A2high MLN-DCs, whereas the E-cadherin-treated DCs did not. Immobilized VCAM-1 and semaphorin 7?A exerted effects similar to those of E-cadherin. Soluble anti-integrin ?1 antibodies or inhibitors of integrin signaling molecules suppressed the effects of these immobilized proteins, whereas immobilized anti-integrin ?1 antibodies enhanced the GM-CSF/Am80-induced ALDH1A2 expression without inducing proinflammatory cytokines. Sequential stimulation of splenic pre-DCs with GM-CSF/Am80 and immobilized E-cadherin or anti-integrin ?1 antibody also induced differentiation to mature DCs with high ALDH activity. The E-cadherin-treated BM-DCs induced gut-tropic Foxp3+ T cells and alleviated DSS-induced colitis, whereas the TLR-L-treated DCs aggravated DSS-induced colitis. The results suggest that integrin ?1-mediated signals contribute to the differentiation and maturation of RA-producing anti-inflammatory DCs.
Project description:The C-type lectin receptor blood dendritic cell Ag 2 (BDCA2) is expressed exclusively on human plasmacytoid DCs (pDCs) and plays a role in Ag capture, internalization, and presentation to T cells. We used transgenic mice that express human BDCA2 and anti-BDCA2 mAbs to deliver Ags directly to BDCA2 on pDCs in vivo. Targeting Ag to pDCs in this manner resulted in significant suppression of Ag-specific CD4(+) T cell and Ab responses upon secondary exposure to Ag in the presence of adjuvant. Suppression of Ab responses required both a decrease in effector CD4(+) T cells and preservation of Foxp3(+) regulatory T cells (Tregs). Reduction in Treg numbers following Ag delivery to BDCA2 restored both CD4(+) T cell activation and Ab responses, demonstrating that Tregs were required for the observed tolerance. Our results demonstrate that Ag delivery to pDCs through BDCA2 is an effective method to induce immunological tolerance, which may be useful for treating autoimmune diseases or to inhibit unwanted Ab responses.
Project description:Aspergillus fumigatus, a ubiquitous mold, is a common cause of invasive aspergillosis (IA) in immunocompromised patients. Host defense against IA relies on lung-infiltrating neutrophils and monocyte-derived dendritic cells (Mo-DCs). Here, we demonstrate that plasmacytoid dendritic cells (pDCs), which are prototypically antiviral cells, participate in innate immune crosstalk underlying mucosal antifungal immunity. Aspergillus-infected murine Mo-DCs and neutrophils recruited pDCs to the lung by releasing the CXCR3 ligands, CXCL9 and CXCL10, in a Dectin-1 and Card9- and type I and III interferon signaling-dependent manner, respectively. During aspergillosis, circulating pDCs entered the lung in response to CXCR3-dependent signals. Via targeted pDC ablation, we found that pDCs were essential for host defense in the presence of normal neutrophil and Mo-DC numbers. Although interactions between pDC and fungal cells were not detected, pDCs regulated neutrophil NADPH oxidase activity and conidial killing. Thus, pDCs act as positive feedback amplifiers of neutrophil effector activity against inhaled mold conidia.
Project description:The ?E integrin chain CD103 identifies a subset of migratory dendritic cells (DCs) in the gut, lung, and skin. To gain further understanding of the function of CD103(+) DCs in regulating adaptive immunity in vivo, we coupled ovalbumin (OVA) to the CD103 antibody M290 (M290.OVA). Intraperitoneal injection of M290.OVA induced OVA-specific CD8(+) and CD4(+) T-cell proliferation in lymph nodes (LNs) of wild-type but not CD103(-/-) mice, or in mice depleted of CD11c(+) cells. In the absence of maturation stimuli, systemic antigen targeting to CD103(+) DCs led to tolerance of CD8(+) T cells, whereas coadministration of adjuvant induced cytotoxic T-lymphocyte (CTL) immunity and antibody production. Mucosal intratracheal application of M290.OVA also induced T-cell proliferation in mediastinal LNs, yet the functional outcome was tolerance that inhibited subsequent development of allergic airway inflammation and immunoglobulin E (IgE) responses to inhaled OVA. These findings identify antigen targeting to CD103(+) DCs as a potential strategy to regulate immune responses in nonlymphoid mucosal tissues.
Project description:The liver maintains a tolerogenic environment to avoid unwarranted activation of its resident immune cells upon continuous exposure to food and bacterially derived Ags. However, in response to hepatotropic viral infection, the liver's ability to switch from a hyporesponsive to a proinflammatory environment is mediated by select sentinels within the parenchyma. To determine the contribution of hepatic dendritic cells (DCs) in the activation of naive CD8(+) T cells, we first characterized resident DC subsets in the murine liver. Liver DCs exhibit unique properties, including the expression of CD8? (traditionally lymphoid tissue specific), CD11b, and CD103 markers. In both the steady-state and following viral infection, liver CD103(+) DCs express high levels of MHC class II, CD80, and CD86 and contribute to the high number of activated CD8(+) T cells. Importantly, viral infection in the Batf3(-/-) mouse, which lacks CD8?(+) and CD103(+) DCs in the liver, results in a 3-fold reduction in the proliferative response of Ag-specific CD8(+) T cells. Limiting DC migration out of the liver does not significantly alter CD8(+) T cell responsiveness, indicating that CD103(+) DCs initiate the induction of CD8(+) T cell responses in situ. Collectively, these data suggest that liver-resident CD103(+) DCs are highly immunogenic in response to hepatotropic viral infection and serve as a major APC to support the local CD8(+) T cell response. It also implies that CD103(+) DCs present a promising cellular target for vaccination strategies to resolve chronic liver infections.
Project description:The division of labor between pulmonary phagocytic subsets [macrophage/monocyte and dendritic cell (DC) subpopulations] has been described at the functional level. However, whether these lung phagocytes also display unique spatial distribution remains unclear. Here, to analyze cellular distribution in lung compartments and contacts between phagocyte subpopulations, we established an immunohistochemistry (IHC)-based method to clearly identify murine lung phagocyte subsets in situ based on differential expression of CD11c, CD11b, MHC-II, Langerin and mPDCA-1. Furthermore, we investigated subset-specific functional differences in antigen uptake and spatial changes upon allergic sensitization. Our staining allowed the distinction between alveolar macrophages (AMs), interstitial macrophage (IM) subpopulations, CD11b+ DC subpopulations, CD103+ DCs, and plasmacytoid DCs (pDCs). We identified interstitial regions between airways and around airways as regions of IM/CD11b+ DC/CD103+ DC clusters, where a subset of IMs (IM2) and CD103+ DCs formed intense contacts that decreased upon allergic sensitization. These data indicate functional interactions between both cell types either in steady state or after antigen encounter affecting the development of allergies or tolerance. Furthermore, we observed major antigen uptake in AMs and IMs rather than DC subpopulations that was not restricted to airways and adjacent areas. This will enable to focus future studies to immunologically relevant cellular interactions and to unravel which cells are tipping the balance between pro-inflammatory immune responses or tolerance.