Nr4a receptors are essential for thymic regulatory T cell development and immune homeostasis.

Regulatory T cells (T(reg) cells) develop from progenitor thymocytes after the engagement of T cell antigen receptors (TCRs) with high-affinity ligands, but the underlying molecular mechanisms are still unclear. Here we show that the Nr4a nuclear receptors, which are encoded by immediate-early genes upregulated by TCR stimulation in thymocytes, have essential roles in T(reg) cell development. Mice that lacked all Nr4a factors could not produce T(reg) cells and died early owing to systemic autoimmunity. Nr4a receptors directly activated the promoter of the gene encoding the transcription factor Foxp3, and forced activation of Nr4a receptors bypassed low-strength TCR signaling to drive the T(reg) cell developmental program. Our results suggest that Nr4a receptors have key roles in determining CD4(+) T cell fates in the thymus and thus contribute to immune homeostasis.

Pivotal role of the carbohydrate recognition domain in self-interaction of CLEC4A to elicit the ITIM-mediated inhibitory function in murine conventional dendritic cells in vitro.

C-type lectin receptors (CLRs), pattern recognition receptors (PRRs) with a characteristic carbohydrate recognition domain (CRD) in the extracellular portion, mediate crucial cellular functions upon recognition of glycosylated pathogens and self-glycoproteins. CLEC4A is the only classical CLR that possesses an intracellular immunoreceptor tyrosine-based inhibitory motif (ITIM), which possibly transduces negative signals. However, how CLEC4A exerts cellular inhibition remains unclear. Here, we report that the self-interaction of CLEC4A through the CRD is required for the ITIM-mediated suppressive function in conventional dendritic cells (cDCs). Human type 2 cDCs (cDC2) and monocytes display a higher expression of CLEC4A than cDC1 and plasmacytoid DCs (pDCs) as well as B cells. The extracellular portion of CLEC4A specifically binds to a murine cDC cell line expressing CLEC4A, while its extracellular portion lacking the N-glycosylation site or the EPS motif within the CRD reduces their association. Furthermore, the deletion of the EPS motif within the CRD or ITIM in CLEC4A almost completely impairs its suppressive effect on the activation of the murine cDC cell line, whereas the absence of the N-glycosylation site within the CRD exhibits partial inhibition on their activation. On the other hand, antagonistic monoclonal antibody (mAb) to CLEC4A, which inhibits the self-interaction of CLEC4A and its downstream signaling in murine transfectants, enhances the activation of monocytes and monocyte-derived immature DCs upon stimulation with a Toll-like receptor (TLR) ligand. Thus, our findings suggest a pivotal role of the CRD in self-interaction of CLEC4A to elicit the ITIM-mediated inhibitory signal for the control of the function of cDCs.

Plasmacytoid dendritic cells are crucial for the initiation of inflammation and T cell immunity in vivo.

Plasmacytoid dendritic cells (pDCs) are characterized as type I interferon-producing cells that engage endosomal toll-like receptors (TLRs) and exclusively express sialic acid binding Ig-like lectin (Siglec)-H. However, their role in vivo remains unclear. Here we report a critical role for pDCs in the regulation of inflammation and T cell immunity in vivo by using gene-targeted mice with a deficiency of Siglec-H and conditional ablation of pDCs. pDCs were required for inflammation triggered by a TLR ligand as well as by bacterial and viral infections. pDCs controlled homeostasis of effector and regulatory CD4(+) T cells. Upon antigenic stimulation and microbial infection, pDCs suppressed the induction of CD4(+) T cell responses and participated in the initiation of CD8(+) T cell responses. Furthermore, Siglec-H appeared to modulate the function of pDCs in vivo. Thus, our findings highlight previously unidentified roles of pDCs and the regulation of their function for the control of innate and adaptive immunity.

Critical role of plasmacytoid dendritic cells in induction of oral tolerance.

BACKGROUND: Exposure to dietary constituents through the mucosal surface of the gastrointestinal tract generates oral tolerance that prevents deleterious T cell-mediated immunity. Although oral tolerance is an active process that involves emergence of CD4+ forkhead box p3 (Foxp3)+ regulatory T (Treg) cells in gut-associated lymphoid tissues (GALTs) for suppression of effector T (Teff) cells, how antigen-presenting cells initiate this process remains unclear. OBJECTIVE: We sought to determine the role of plasmacytoid dendritic cells (pDCs), which are known as unconventional antigen-presenting cells, in establishment of oral tolerance. METHODS: GALT-associated pDCs in wild-type mice were examined for their ability to induce differentiation of CD4+ Teff cells and CD4+Foxp3+ Treg cells in vitro. Wild-type and pDC-ablated mice were fed oral antigen to compare their intestinal generation of CD4+Foxp3+ Treg cells and induction of oral tolerance to protect against Teff cell-mediated allergic inflammation. RESULTS: GALT-associated pDCs preferentially generate CD4+Foxp3+ Treg cells rather than CD4+ Teff cells, and such generation requires an autocrine loop of TGF-ß for its robust production. A deficiency of pDCs abrogates antigen-specific de novo generation of CD4+Foxp3+ Treg cells occurring in GALT after antigenic feeding. Furthermore, the absence of pDCs impairs development of oral tolerance, which ameliorates the progression of delayed-type hypersensitivity and systemic anaphylaxis, as well as allergic asthma, accompanied by an enhanced antigen-specific CD4+ Teff cell response and antibody production. CONCLUSION: pDCs are required for establishing oral tolerance to prevent undesirable allergic responses, and they might serve a key role in maintaining gastrointestinal immune homeostasis.

Regulatory Dendritic Cells.

Dendritic cells (DCs) comprise heterogeneous subsets, functionally classified into conventional DCs (cDCs) and plasmacytoid DCs (pDCs). DCs are considered to be essential antigen (Ag)-presenting cells (APCs) that play crucial roles in activation and fine-tuning of innate and adaptive immunity under inflammatory conditions, as well as induction of immune tolerance to maintain immune homeostasis under steady-state conditions. Furthermore, DC functions can be modified and influenced by stimulation with various extrinsic factors, such as ligands for pattern-recognition receptors (PRRs) and cytokines. On the other hand, treatment of DCs with certain immunosuppressive drugs and molecules leads to the generation of tolerogenic DCs that show downregulation of both the major histocompatibility complex (MHC) and costimulatory molecules, and not only show defective T-cell activation, but also possess tolerogenic properties including the induction of anergic T-cells and regulatory T (Treg) cells. To develop an effective strategy for Ag-specific intervention of T-cell-mediated immune disorders, we have previously established the modified DCs with moderately high levels of MHC molecules that are defective in the expression of costimulatory molecules that had a greater immunoregulatory property than classical tolerogenic DCs, which we therefore designated as regulatory DCs (DCreg). Herein, we integrate the current understanding of the role of DCs in the control of immune responses, and further provide new information of the characteristics of tolerogenic DCs and DCreg, as well as their regulation of immune responses and disorders.

Aryl hydrocarbon receptor plays protective roles in ConA-induced hepatic injury by both suppressing IFN-γ expression and inducing IL-22.

The aryl hydrocarbon receptor (AhR), a ligand-activated nuclear transcription factor, is known to mediate the toxic and carcinogenic effects of various environmental pollutants, while AhR has been shown to protect animals from various types of tissue injury. ConA-induced hepatitis is known as a mouse model of acute liver injury. Here, we found a protective role of AhR in ConA-induced hepatitis. AhR is induced in the liver during ConA-induced hepatitis, and Ahr (-/-) mice were highly sensitive to this model. Bone marrow chimera experiments indicate that Ahr (-/-) hematopoietic cells are responsible for hypersensitivity to ConA-induced hepatitis. We found that IFN-γ from invariant NKT cells was up-regulated and IL-22 from innate lymphoid cells (ILCs) was abolished in Ahr (-/-) mice. In addition, IL-22 production was still observed in Rag2 (-/-) mice but it was severely reduced in Ahr (-/-) Rag2 (-/-) mice. ConA-induced IL-22 production was also dependent on retinoic acid-related orphan receptor γt. These results show that AhR has crucial protective roles in ConA-induced liver injury via promoting IL-22 production from ILCs and suppressing IFN-γ expression from NKT cells.

Smad2/3 and IRF4 play a cooperative role in IL-9-producing T cell induction.

IL-9 is a pleiotropic cytokine that can regulate autoimmune and allergic responses. Th9 cells can develop from naive T cells or Th2 cells through stimulation by TGF-ß in vitro. In this study, we demonstrated that Smad2 and Smad3 are necessary for IL-9 production from T cells in an OVA-induced asthma model using T cell-specific Smad2- and Smad3-deficient mice. Smad2 and Smad3 were also redundantly essential for TGF-ß signaling to induce histone modifications for Il9 transcription. Although Smad2/3 was recruited to the Il9 promoter by TGF-ß stimulation, they are not sufficient to activate the Il9 promoter. By the screening the transcription factors, we found that IFN regulatory factor 4 (IRF4) was essential for the Smad2/3-mediated Il9 promoter activation. In addition, Smad2/3 physically interacted with IRF4, and Smad2/3 did not bind to the Il9 promoter and could not induce Th9 in IRF4-deficient T cells. Similarly, IRF4 could not stimulate Il9 transcription in the absence of Smad2/3, and TGF-ß enhanced IRF4 recruitment to the Il9 promoter in a Smad2/3-dependent manner. We propose that Smad2/3 and IRF4 cooperatively transactivate the Il9 promoter and play an important role in regulating allergic immune responses by inducing Th9 cells.

Conditional ablation of CD205+ conventional dendritic cells impacts the regulation of T-cell immunity and homeostasis in vivo.

Dendritic cells (DCs) are composed of multiple subsets that play a dual role in inducing immunity and tolerance. However, it is unclear how CD205(+) conventional DCs (cDCs) control immune responses in vivo. Here we generated knock-in mice with the selective conditional ablation of CD205(+) cDCs. CD205(+) cDCs contributed to antigen-specific priming of CD4(+) T cells under steady-state conditions, whereas they were dispensable for antigen-specific CD4(+) T-cell responses under inflammatory conditions. In contrast, CD205(+) cDCs were required for antigen-specific priming of CD8(+) T cells to generate cytotoxic T lymphocytes (CTLs) mediated through cross-presentation. Although CD205(+) cDCs were involved in the thymic generation of CD4(+) regulatory T cells (Tregs), they maintained the homeostasis of CD4(+) Tregs and CD4(+) effector T cells in peripheral and mucosal tissues. On the other hand, CD205(+) cDCs were involved in the inflammation triggered by Toll-like receptor ligand as well as bacterial and viral infections. Upon microbial infections, CD205(+) cDCs contributed to the cross-priming of CD8(+) T cells for generating antimicrobial CTLs to efficiently eliminate pathogens, whereas they suppressed antimicrobial CD4(+) T-cell responses. Thus, these findings reveal a critical role for CD205(+) cDCs in the regulation of T-cell immunity and homeostasis in vivo.

Loss of Sprouty4 in T cells ameliorates experimental autoimmune encephalomyelitis in mice by negatively regulating IL-1ß receptor expression.

Th17 cells, which have been implicated in autoimmune diseases, require IL-6 and TGF-ß for early differentiation. To gain pathogenicity, however, Th17 cells require IL-1ß and IL-23. The underlying mechanism by which these confer pathogenicity is not well understood. Here we show that Sprouty4, an inhibitor of the PLCγ-ERK pathway, critically regulates inflammatory Th17 (iTh17) cell differentiation. Sprouty4-deficient mice, as well as mice adoptively transferred with Sprouty4-deficient T cells, were resistant to experimental autoimmune encephalitis (EAE) and showed decreased Th17 cell generation in vivo. In vitro, Sprouty4 deficiency did not severely affect TGF-ß/IL-6-induced Th17 cell generation but strongly impaired Th17 differentiation induced by IL-1/IL-6/IL-23. Analysis of Th17-related gene expression revealed that Sprouty4-deficient Th17 cells expressed lower levels of IL-1R1 and IL-23R, while RORγt levels were similar. Consistently, overexpression of Sprouty4 or pharmacological inhibition of ERK upregulated IL-1R1 expression in primary T cells. Thus, Sprouty4 and ERK play a critical role in developing iTh17 cells in Th17 cell-driven autoimmune diseases.

Clec4A4 Acts as a Negative Immune Checkpoint Regulator to Suppress Antitumor Immunity.

Clec4A4 is a C-type lectin receptor (CLR) exclusively expressed on murine conventional dendritic cells (cDC) to regulate their activation status. However, the functional role of murine Clec4A4 (mClec4A4) in antitumor immunity remains unclear. Here, we show that mClec4A4 serves as a negative immune checkpoint regulator to impair antitumor immune responses. Deficiency of mClec4A4 lead to a reduction in tumor development, accompanied by enhanced antitumor immune responses and amelioration of the immunosuppressive tumor microenvironment (TME) mediated through the enforced activation of cDCs in tumor-bearing mice. Furthermore, antagonistic mAb to human CLEC4A (hCLEC4A), which is the functional orthologue of mClec4A4, exerted protection against established tumors without any apparent signs of immune-related adverse events in hCLEC4A-transgenic mice. Thus, our findings highlight the critical role of mClec4A4 expressed on cDCs as a negative immune checkpoint molecule in the control of tumor progression and provide support for hCLEC4A as a potential target for immune checkpoint blockade in tumor immunotherapy.

Gut dysbiosis promotes the breakdown of oral tolerance mediated through dysfunction of mucosal dendritic cells.

While dysbiosis in the gut is implicated in the impaired induction of oral tolerance generated in mesenteric lymph nodes (MesLNs), how dysbiosis affects this process remains unclear. Here, we describe that antibiotic-driven gut dysbiosis causes the dysfunction of CD11c+CD103+ conventional dendritic cells (cDCs) in MesLNs, preventing the establishment of oral tolerance. Deficiency of CD11c+CD103+ cDCs abrogates the generation of regulatory T cells in MesLNs to establish oral tolerance. Antibiotic treatment triggers the intestinal dysbiosis linked to the impaired generation of colony-stimulating factor 2 (Csf2)-producing group 3 innate lymphoid cells (ILC3s) for regulating the tolerogenesis of CD11c+CD103+ cDCs and the reduced expression of tumor necrosis factor (TNF)-like ligand 1A (TL1A) on CD11c+CD103+ cDCs for generating Csf2-producing ILC3s. Thus, antibiotic-driven intestinal dysbiosis leads to the breakdown of crosstalk between CD11c+CD103+ cDCs and ILC3s for maintaining the tolerogenesis of CD11c+CD103+ cDCs in MesLNs, responsible for the failed establishment of oral tolerance.

Histone 3 lysine 9 (H3K9) methyltransferase recruitment to the interleukin-2 (IL-2) promoter is a mechanism of suppression of IL-2 transcription by the transforming growth factor-ß-Smad pathway.

Suppression of IL-2 ßproduction from T cells is an important process for the immune regulation by TGF-ß. However, the mechanism by which this suppression occurs remains to be established. Here, we demonstrate that Smad2 and Smad3, two major TGF-ß-downstream transcription factors, are redundantly essential for TGF-ß-mediated suppression of IL-2 production in CD4(+) T cells using Smad2- and Smad3-deficient T cells. Both Smad2 and Smad3 were recruited into the proximal region of the IL-2 promoter in response to TGF-ß. We then investigated the histone methylation status of the IL-2 promoter. Although both histone H3 lysine 9 (H3K9) and H3K27 trimethylation have been implicated in gene silencing, only H3K9 trimethylation was increased in the proximal region of the IL-2 promoter in a Smad2/3-dependent manner, whereas H3K27 trimethylation was not. The H3K9 methyltransferases Setdb1 and Suv39h1 bound to Smad3 and suppressed IL-2 promoter activity in collaboration with Smad3. Overexpression of Suv39h1 in 68-41 T cells strongly inhibited IL-2 production in response to T cell receptor stimulation irrespective of the presence or absence of TGF-ß, whereas Setdb1 overexpression only slightly suppressed IL-2 production. Silencing of Suv39h1 by shRNA reverted the suppressive effect of TGF-ß on IL-2 production. Furthermore, TGF-ß induced Suv39h1 recruitment to the proximal region of the IL-2 promoter in wild type primary T cells; however, this was not observed in Smad2(-/-)Smad3(+/-) T cells. Thus, we propose that Smads recruit H3K9 methyltransferases Suv39h1 to the IL-2 promoter, thereby inducing suppressive histone methylation and inhibiting T cell receptor-mediated IL-2 transcription.

Low dose CP-690,550 (tofacitinib), a pan-JAK inhibitor, accelerates the onset of experimental autoimmune encephalomyelitis by potentiating Th17 differentiation.

Th17 cells, which have been implicated in autoimmune diseases, require STAT3 signaling activated by IL-6 or IL-23 for their development. Other Th1 and Th2 cytokines such as IL-2, IFN-γ and IL-4 strongly suppress Th17 development. Recently, CP-690,550 (tofacitinib), originally developed as a JAK3 inhibitor, has been shown to be effective in phase III clinical trials of rheumatoid arthritis and collagen-induced arthritis (CIA) models, but the precise mechanism of the effect, especially with respect to Th17 cells, is poorly understood. To our surprise, a low dose CP-690,550 was found to accelerate the onset of experimental autoimmune encephalomyelitis (EAE) at a concentration that suppressed CIA. At an early stage after immunization, more IL-17 production was observed in 15mg/kg body weight CP-690,550-treated mice than in untreated mice. In vitro, CP-690,550 inhibited both Th1 and Th2 development, while promoting Th17 differentiation at 10-50nM concentrations. Enhancement of Th17 by CP-690,550 is probably due to suppression of IL-2 signaling, because anti-IL-2 antibodies cancel the Th17-promoting effect of CP-690,550. CP-690,550 selectively inhibited IFN--induced STAT1, IL-4-induced STAT6 and IL-2-induced STAT5 at 3-30nM, while suppression of IL-6-induced STAT3 phosphorylation required a concentration greater than 100nM. In HEK293T cells, CP-690,550 less effectively suppressed JAK1-mediated STAT3 phosphorylation compared with JAK3. These results suggest that CP-690,550 has a different effects among JAKs and STATs, thereby affecting helper T cell differentiation, and murine autoimmune disease models.

Crucial roles of B7-H1 and B7-DC expressed on mesenteric lymph node dendritic cells in the generation of antigen-specific CD4+Foxp3+ regulatory T cells in the establishment of oral tolerance.

Oral tolerance is a key feature of intestinal immunity, generating systemic tolerance to fed antigens. However, the molecular mechanism mediating oral tolerance remains unclear. In this study, we examined the role of the B7 family members of costimulatory molecules in the establishment of oral tolerance. Deficiencies of B7-H1 and B7-DC abrogated the oral tolerance, accompanied by enhanced antigen-specific CD4(+) T-cell response and IgG(1) production. Mesenteric lymph node (MLN) dendritic cells (DCs) displayed higher levels of B7-H1 and B7-DC than systemic DCs, whereas they showed similar levels of CD80, CD86, and B7-H2. MLN DCs enhanced the antigen-specific generation of CD4(+)Foxp3(+) inducible regulatory T cells (iT(regs)) from CD4(+)Foxp3(-) T cells rather than CD4(+) effector T cells (T(eff)) relative to systemic DCs, owing to the dominant expression of B7-H1 and B7-DC. Furthermore, the antigen-specific conversion of CD4(+)Foxp3(-) T cells into CD4(+)Foxp3(+) iT(regs) occurred in MLNs greater than in peripheral organs during oral tolerance under steady-state conditions, and such conversion required B7-H1 and B7-DC more than other B7 family members, whereas it was severely impaired under inflammatory conditions. In conclusion, our findings suggest that B7-H1 and B7-DC expressed on MLN DCs are essential for establishing oral tolerance through the de novo generation of antigen-specific CD4(+)Foxp3(+) iT(regs).

Spatiotemporal expression of HMGB2 regulates cell proliferation and hepatocyte size during liver regeneration.

Liver regeneration is an extraordinarily complex process involving a variety of factors; however, the role of chromatin protein in hepatocyte proliferation is largely unknown. In this study, we investigated the functional role of high-mobility group box 2 (HMGB2), a chromatin protein in liver regeneration using wild-type and HMGB2-knockout (KO) mice. Liver tissues were sampled after 70% partial hepatectomy (PHx), and analyzed by immunohistochemistry, western blotting and flow cytometry using various markers of cell proliferation. In WT mice, hepatocyte proliferation was strongly correlated with the spatiotemporal expression of HMGB2; however, cell proliferation was significantly delayed in hepatocytes of HMGB2-KO mice. Quantitative PCR demonstrated that cyclin D1 and cyclin B1 mRNAs were significantly decreased in HMGB2-KO mice livers. Interestingly, hepatocyte size was significantly larger in HMGB2-KO mice at 36-72 h after PHx, and these results suggest that hepatocyte hypertrophy appeared in parallel with delayed cell proliferation. In vitro experiments demonstrated that cell proliferation was significantly decreased in HMGB2-KO cells. A significant delay in cell proliferation was also found in HMGB2-siRNA transfected cells. In summary, spatiotemporal expression of HMGB2 is important for regulation of hepatocyte proliferation and cell size during liver regeneration.

Naturally occurring regulatory dendritic cells regulate murine cutaneous chronic graft-versus-host disease.

Chronic graft-versus-host disease (cGVHD) is a limiting factor in allogeneic hematopoietic stem cell transplantation (alloHSCT) for the treatment of leukemia and other malignancies. Relative to the process that initiates and promotes cGVHD, the regulation is poorly understood. In this study, we examined the role of naturally occurring regulatory dendritic cells (DC(regs)) in murine major histocompatibility complex (MHC)-compatible and multiple minor histocompatibility antigen (miHAg)-incompatible model of cGVHD in alloHSCT. DC(regs) generated from bone marrow in vitro (BM-DC(regs)) exclusively expressed CD200 receptor 3 (CD200R3), which exerted a suppressive function in the Ag-specific CD4(+) T-cell response. CD49(+)CD200R3(+) cells showed similarities in phenotype and function to BM-DC(regs), which formally distinguishes them from other leukocytes, suggesting that they are the natural counterpart of BM-DC(regs). Treatment of the recipient mice after alloHSCT with the recipient-type CD49(+)CD200R3(+) cells as well as BM-DC(regs) protected against cGVHD, and the protection was associated with the generation of Ag-specific anergic CD4(+) T cells as well as CD4(+)CD25(+)Foxp3(+) regulatory T cells (T(regs)) from donor-derived alloreactive CD4(+)CD25(-)Foxp3(-) T cells. In addition, the depletion of CD49(+)CD200R3(+) cells before alloHSCT enhanced the progression of cGVHD. In conclusion, CD49(+)CD200R3(+) cells act as naturally occurring DC(regs) to regulate the pathogenesis of cGVHD in alloHSCT mediated through the control of the transplanted alloreactive CD4(+) T cells.

Congenital Deficiency of Conventional Dendritic Cells Promotes the Development of Atopic Dermatitis-Like Inflammation.

Atopic dermatitis (AD) is a common pruritic inflammatory skin disease characterized by impaired epidermal barrier function and dysregulation of Thelper-2 (TH2)-biased immune responses. While the lineage of conventional dendritic cells (cDCs) are implicated to play decisive roles in T-cell immune responses, their requirement for the development of AD remains elusive. Here, we describe the impact of the constitutive loss of cDCs on the progression of AD-like inflammation by using binary transgenic (Tg) mice that constitutively lacked CD11chi cDCs. Unexpectedly, the congenital deficiency of cDCs not only exacerbates the pathogenesis of AD-like inflammation but also elicits immune abnormalities with the increased composition and function of granulocytes and group 2 innate lymphoid cells (ILC2) as well as B cells possibly mediated through the breakdown of the Fms-related tyrosine kinase 3 ligand (Flt3L)-mediated homeostatic feedback loop. Furthermore, the constitutive loss of cDCs accelerates skin colonization of Staphylococcus aureus (S. aureus), that associated with disease flare. Thus, cDCs maintains immune homeostasis to prevent the occurrence of immune abnormalities to maintain the functional skin barrier for mitigating AD flare.

Essential role of submandibular lymph node dendritic cells in protective sublingual immunotherapy against murine allergy.

While sublingual immunotherapy (SLIT) is known as an allergen-specific treatment for type-1 allergies, how it controls allergic pathogenesis remains unclear. Here, we show the prerequisite role of conventional dendritic cells in submandibular lymph nodes (ManLNs) in the effectiveness of SLIT for the treatment of allergic disorders in mice. Deficiency of conventional dendritic cells or CD4+Foxp3+ regulatory T (Treg) cells abrogates the protective effect of SLIT against allergic disorders. Furthermore, sublingual antigenic application primarily induces antigen-specific CD4+Foxp3+ Treg cells in draining ManLNs, in which it is severely impaired in the absence of cDCs. In ManLNs, migratory CD11b+ cDCs are superior to other conventional dendritic cell subsets for the generation of antigen-specific CD4+Foxp3+ Treg cells, which is reflected by their dominancy in the tolerogenic features to favor this program. Thus, ManLNs are privileged sites in triggering mucosal tolerance mediating protect effect of SLIT on allergic disorders that requires a tolerogenesis of migratory CD11b+ conventional dendritic cells.

Author Correction: Pivotal role of CD103 in the development of psoriasiform dermatitis.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Pivotal role of CD103 in the development of psoriasiform dermatitis.

The integrin αE known as CD103 binds integrin ß7 to form the complete heterodimeric integrin molecule αEß7. CD103 is mainly expressed by lymphocytes within epithelial tissues of intestine, lung, and skin as well as subsets of mucosal and dermal conventional dendritic cells (cDCs). CD103 has been originally implicated in the attachment of lymphocytes to epithelium in the gut and skin through the interaction with E-cadherin expressed on intestinal epithelial cells, keratinocytes, and Langerhans cells (LCs). However, an impact of CD103 on the cutaneous immune responses and the development of inflammatory skin diseases remains elusive. Here, we report that CD103 regulates the development of psoriasiform dermatitis through the control of the function of cDCs. Deficiency in CD103 exacerbates psoriasiform dermatitis, accompanied by excessive epidermal hyperplasia and infiltration of inflammatory leukocytes. Furthermore, deficiency in CD103 not only accelerates the production of proinflammatory cytokines in psoriatic lesions but also promotes the generation of lymphocytes producing interleukin (IL)-17 in the skin-draining peripheral lymph nodes (PLNs). Under the deficiency in CD103, cDCs localized in PLNs enhance cytokine production following activation. Thus, our findings reveal a pivotal role for CD103 in the control of the function of cDCs to regulate cutaneous inflammation in psoriasiform dermatitis.