Langerhans cells mediate the skin-induced tolerance to ovalbumin via Langerin in a murine model.

BACKGROUND: Epicutaneous sensitization is an important route of immunization for allergens in atopic diseases; however, studies have also shown that application with protein on the intact skin induces antigen-specific tolerance. Langerhans cells (LCs) play an immunosuppressive role in several inflammatory skin diseases and mouse models, and the role of LCs in the skin-induced tolerance is not fully understood. METHODS: Langerin-DTA mice that were deficient in LCs were utilized to produce the model of skin-induced tolerance to ovalbumin (OVA). Binding of Langerin to OVA was analyzed by enzyme-linked immunosorbent assay, flow cytometry, and immunofluorescence. Homozygous Langerin-DTR mice that were deficient in Langerin were introduced to assess the role of Langerin in the skin-induced tolerance. RESULTS: Application with OVA onto the intact, but not tape-stripped, skin attenuated the production of OVA-specific IgE, IgG1, and IgG2a induced by subsequent subcutaneous immunization with OVA, and the inhibitory effects were abolished in Langerin-DTA mice. In contrast to the tape-stripped skin, the intact skin induced the production of IL-10 by LCs in draining lymph node after application with OVA. Langerin could bind OVA, and homozygous Langerin-DTR mice demonstrated similar humoral and cellular immune responses in the model of skin-induced tolerance compared to wide-type mice. CONCLUSION: Our data suggested that LCs were critical in the intact skin-induced tolerance to protein antigen via Langerin, and LCs might be targeted via Langerin to regulate the immune responses in systemic and (or) skin inflammatory diseases.

Immunometabolic phenotype of BV-2 microglia cells upon murine cytomegalovirus infection.

Microglia are resident brain macrophages with key roles in development and brain homeostasis. Cytomegalovirus (CMV) readily infects microglia cells, even as a possible primary target of infection in development. Effects of CMV infection on a cellular level in microglia are still unclear; therefore, the aim of this research was to assess the immunometabolic changes of BV-2 microglia cells following the murine cytomegalovirus (MCMV) infection. In light of that aim, we established an in vitro model of ramified BV-2 microglia (BV-2∅FCS, inducible nitric oxide synthase (iNOSlow), arginase-1 (Arg-1high), mannose receptor CD206high, and hypoxia-inducible factor 1α (HIF-1αlow)) to better replicate the in vivo conditions by removing FCS from the cultivation media, while the cells cultivated in 10% FCS DMEM displayed an ameboid morphology (BV-2FCS high, iNOShigh, Arg-1low, CD206low, and HIF-1αhigh). Experiments were performed using both ramified and ameboid microglia, and both of them were permissive to productive viral infection. Our results indicate that MCMV significantly alters the immunometabolic phenotypic properties of BV-2 microglia cells through the manipulation of iNOS and Arg-1 expression patterns, along with an induction of a glycolytic shift in the infected cell cultures.

Analysis of MCFD2- and LMAN1-deficient mice demonstrates distinct functions in vivo.

The LMAN1-MCFD2 complex serves as a cargo receptor for efficient transport of factor V (FV) and FVIII from the endoplasmic reticulum (ER) to the Golgi. Genetic deficiency of LMAN1 or MCFD2 in humans results in the moderate bleeding disorder combined FV and FVIII deficiency, with a similar phenotype previously observed in LMAN1-deficient mice. We now report that MCFD2-deficient mice generated by gene targeting also demonstrate reduced plasma FV and FVIII, with levels lower than those in LMAN1-deficient mice, similar to previous observations in LMAN1- and MCDF2-deficient humans. Surprisingly, FV and FVIII levels in doubly deficient mice match the higher levels observed in LMAN1-deficient mice. In contrast to the strain-specific partial lethality previously observed in LMAN1-null mice, MCFD2-null mice demonstrate normal survival in different genetic backgrounds, although doubly deficient mice exhibit partial embryonic lethality comparable to LMAN1-deficient mice. These results suggest that an alternative pathway is responsible for FV/FVIII secretion in doubly deficient mice and distinct cargo-specific functions for LMAN1 and MCFD2 within the ER-to-Golgi secretory pathway. We also observed decreased plasma levels of α1-antitrypsin (AAT) in male mice for all 3 groups of deficient mice. Comparable accumulation of AAT was observed in hepatocyte ER of singly and doubly deficient mice, demonstrating a role for LMAN1 and MCFD2 in efficient ER exit of AAT.

Sequential BMP7/TGF-ß1 signaling and microbiota instruct mucosal Langerhans cell differentiation.

Mucosal Langerhans cells (LCs) originate from pre-dendritic cells and monocytes. However, the mechanisms involved in their in situ development remain unclear. Here, we demonstrate that the differentiation of murine mucosal LCs is a two-step process. In the lamina propria, signaling via BMP7-ALK3 promotes translocation of LC precursors to the epithelium. Within the epithelium, TGF-ß1 finalizes LC differentiation, and ALK5 is crucial to this process. Moreover, the local microbiota has a major impact on the development of mucosal LCs, whereas LCs in turn maintain mucosal homeostasis and prevent tissue destruction. These results reveal the differential and sequential role of TGF-ß1 and BMP7 in LC differentiation and highlight the intimate interplay of LCs with the microbiota.

Mannose-Binding Lectin Protein Deficiency Among Patients with Primary Immunodeficiency Disease Receiving IVIG Therapy.

BACKGROUND: Primary immunodeficiencies (PIDs) are inherited disorders in which one or several components of the immune system are defective. Immunoglobulin replacement therapy is the mainstay of treatment for patients with impaired antibody production. However, recurrent infections would continue to occur in some patients due to the other high frequent concomitant defects, such as mannose-binding lectin (MBL) deficiency. METHODS: A total of 51 PID patients participated in this cross-sectional study. A detailed questionnaire was completed by interviewing patients in order to record demographic, clinical and laboratory data. The levels of MBL were determined in the serums of patients by a sandwich enzyme-linked immunosorbent assay (ELISA) technique. RESULTS: MBL deficiency was found in 29.4% of cases; 11.8% patients had mild, 3.9% patients had moderate and 13.7% patients had severe MBL deficiency. In patients with MBL deficiency, the rate of meningitis, sepsis, pneumonia, and otitis media was higher than patients with normal MBL levels. Immunoglobulin replacement therapy reduced the rate of infectious complications in PID patients; however, these reductions were more apparent in patients with normal MBL levels than patients with MBL deficiency. CONCLUSION: Antibody deficient patients with a concomitant immune defect in MBL production have higher rates of recurrent infections despite receiving Immunoglobulin replacement therapy.

N-glycosylation converts non-glycoproteins into mannose receptor ligands and reveals antigen-specific T cell responses in vivo.

N-glycosylation is generally accepted to enhance the immunogenicity of antigens because of two main reasons. First, the attachment of glycans enables recognition by endocytic receptors like the mannose receptor (MR) and hence increased uptake by dendritic cells (DCs). Second, foreign glycans are postulated to be immunostimulatory and their recognition could induce DC activation. However, a direct comparison between the immunogenicity of N-glycosylated vs. de-glycosylated proteins in vivo and a direct effect of N-glycosylated antigens on the intrinsic capacity of DCs to activate T cells have not been assessed so far.To analyze whether enforced N-glycosylation is a suited strategy to enhance the immunogenicity of non-glycosylated antigens for vaccination studies, we targeted non-glycoproteins towards the MR by introduction of artificial N-glycosylation using the methylotrophic yeast Komagataella phaffii (previously termed Pichia pastoris). We could demonstrate that the introduction of a single N-X-S/T motif was sufficient for efficient MR-binding and internalization. However, addition of N-glycosylated proteins neither influenced DC maturation nor their general capacity to activate T cells, pointing out that enforced N-glycosylation does not increase the immunogenicity of the antigen per se. Additionally, increased antigen-specific cytotoxic T cell responses in vivo after injection of N-glycosylated compared to de-glycosylated proteins were observed but this effect strongly depended on the epitope tested. A beneficial effect of N-glycosylation on antibody production could not be detected, which might be due to MR-cross-linking on DCs and to concomitant differences in IL-6 production by CD4+ T cells.These observations point out that the effect of N-glycosylation on antigen immunogenicity can vary between different antigens and therefore might have important implications for the development of vaccines using K. phaffii.

LMAN1 (ERGIC-53) is a potential carrier protein for matrix metalloproteinase-9 glycoprotein secretion.

Matrix metalloproteinase-9 (MMP-9) is a secreted glycoprotein with a major role in shaping the extracellular matrix and a detailed understanding of the secretory mechanism could help identify methods to correct diseases resulting from dysregulation of secretion. MMP-9 appears to follow a canonical secretory pathway through a quality control cycle in the endoplasmic reticulum (ER) before transport of the properly folded protein to the Golgi apparatus and beyond for secretion. Through a complementation assay, we determined that LMAN1, a well-studied lectin-carrier protein, interacts with a secretion-competent N-glycosylated MMP-9 in the ER while N-glycosylation-deficient secretion-compromised MMP-9 does not. In contrast, co-immunoprecipitation demonstrated protein interaction between LMAN1 and secretion-compromised N-glycosylation-deficient MMP-9. MMP-9 secretion was reduced in the LMAN1 knockout cell line compared to control cells confirming the functional role of LMAN1. These observations support the role of LMAN1 as a lectin-carrier protein mediating efficient MMP-9 secretion.

Phospholipase A2 inhibits cisplatin-induced acute kidney injury by modulating regulatory T cells by the CD206 mannose receptor.

Previously, we found that Foxp3-expressing CD4(+) regulatory T (Treg) cells attenuate cisplatin-induced acute kidney injury in mice and that bee venom and its constituent phospholipase A2 (PLA2) are capable of modulating Treg cells. Here we tested whether PLA2 could inhibit cisplatin-induced acute kidney injury. As a result of treatment with PLA2, the population of Treg cells was significantly increased, both in vivo and in vitro. PLA2-injected mice showed reduced levels of serum creatinine, blood urea nitrogen, renal tissue damage, and pro-inflammatory cytokine production upon cisplatin administration. These renoprotective effects were abolished by depletion of Treg cells. Furthermore, PLA2 bound to CD206 mannose receptors on dendritic cells, essential for the PLA2-mediated protective effects on renal dysfunction. Interestingly, PLA2 treatment increased the secretion of IL-10 in the kidney from normal mice. Foxp3(+)IL-10(+) cells and CD11c(+)IL-10(+) cells were increased by PLA2 treatment. The anticancer effects of repeated administrations of a low dose of cisplatin were not affected by PLA2 treatment in a tumor-bearing model. Thus, PLA2 may prevent inflammatory responses in cisplatin-induced acute kidney injury by modulating Treg cells and IL-10 through the CD206 mannose receptor.

Plasma-derived mannose-binding lectin shows a direct interaction with C1-inhibitor.

MBL-deficiency has been associated with an increased frequency and severity of infection, in particular in children and under immunocompromized conditions. In an open uncontrolled safety and pharmacokinetic MBL-substitution study using plasma-derived MBL (pdMBL) in MBL-deficient pediatric oncology patients, we found that despite MBL trough levels above 1.0µg/ml MBL functionality was not efficiently restored upon ex vivo testing. PdMBL showed C4-converting activity by itself, indicating the presence of MASPs. Upon incubation of pdMBL with MBL-deficient sera this C4-converting activity was significantly reduced. Depletion of the MASPs from pdMBL, paradoxically, restored the C4-converting activity. Subsequent depletion or inhibition of C1-inh, the major inhibitor of the lectin pathway, in the recipient serum restored the C4-converting activity as well. Complexes between MBL/MASPs and C1-inh (MMC-complexes) were detected after ex vivo substitution of MBL-deficient serum with pdMBL. These MMC-complexes could also be detected in the sera of the patients included in the MBL-substitution study shortly after pdMBL infusion. Altogether, we concluded that active MBL-MASP complexes in pdMBL directly interact with C1-inh in the recipient, leading to the formation of a multimolecular complex between C1-inh and MBL/MASPs, in contrast to the classical pathway where C1r and C1s are dissociated from C1q by C1-inh. Because of the presence of activated MASPs in the current pdMBL products efficient MBL-mediated host protection cannot be expected because of the neutralizing capacity by C1-inh.

Role of the mannose receptor in phagocytosis of Enterococcus faecalis strain EC-12 by antigen-presenting cells.

The aim of this study was to clarify the phagocytic mechanisms of a heat-killed cell preparation of Enterococcus faecalis strain EC-12 (EC-12) by antigen-presenting cells (APCs). Fluorescein isothiocyanate (FITC)-labeled EC-12 was cocultured with peritoneal macrophage and the amount of EC-12 phagocytosed by peritoneal macrophages was measured using a microplate fluorometer. Peritoneal macrophages from toll-like receptor (TLR)2-, TLR7-, and MyD88-deficient knockout (KO) mice exhibited similar levels of EC-12 phagocytosis to those from wild-type mice. Similarly, dectin-1 neutralization of peritoneal macrophages had no effect on EC-12 phagocytosis. However, blockade of the mannose receptor (MR) significantly decreased the amount of EC-12 phagocytosed by peritoneal macrophages; the same effect was observed in bone marrow-derived macrophages and dendritic cells. Our findings suggest that MR plays a major role in EC-12 phagocytosis by the APCs.

Functionalization of polyanhydride microparticles with di-mannose influences uptake by and intracellular fate within dendritic cells.

Innovative vaccine delivery platforms can facilitate the development of effective single-dose treatment regimens to control emerging and re-emerging infectious diseases. Polyanhydride microparticles are promising vaccine delivery vehicles due to their ability to stably maintain antigens, provide tailored release kinetics and function as adjuvants. A major obstacle for the use of microparticle-based vaccines, however, is their limited uptake by dendritic cells (DCs). In this study, we functionalized the microparticle surface with di-mannose in order to target C-type lectin receptors (CLRs) on DCs. Polyanhydride particles based on sebacic acid (SA), 1,6-bis(p-carboxyphenoxy)hexane (CPH) and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) were evaluated. Co-incubation of di-mannose-functionalized microparticles up-regulated the expression of CLRs on DCs. More importantly, di-mannose functionalization increased the uptake, as measured by the percentage of cells internalizing particles. The uptake of CPH:SA microparticles increased ∼20-fold, from 0.82% (non-functionalized) to 20.2%, and internalization of CPTEG:CPH microparticles increased ∼7-fold from 1.35% (non-functionalized) to 9.3% upon di-mannose functionalization. Both di-mannose-functionalized and non-functionalized particles trafficked to lysosomes. Together, these studies demonstrate that employing rational vaccine design principles, such as the targeting of CLRs on antigen-presenting cells, can enhance delivery of encapsulated antigens and potentially induce a more robust adaptive immune response.

Langerin(neg) conventional dendritic cells produce IL-23 to drive psoriatic plaque formation in mice.

Psoriasis is an autoinflammatory skin disease of unknown etiology. Topical application of Aldara cream containing the Toll-like receptor (TLR)7 agonist Imiquimod (IMQ) onto patients induces flares of psoriasis. Likewise, in mice IMQ triggers pathological changes closely resembling psoriatic plaque formation. Key cytokines like IL-23 and type-I IFN (IFN-I), both being produced mainly by dendritic cells (DCs), have been implicated in psoriasis. Although plasmacytoid DCs (pDCs) are the main source of IFNα and thought to initiate disease, conventional DCs (cDCs) appear to maintain the psoriatic lesions. Any role of cDCs during lesion formation remains elusive. Here, we report that selective activation of TLR7 signaling specifically in CD11c(+) DCs was sufficient to induce psoriasiform skin disease in mice. Intriguingly, both pDCs and the IFN-I pathway were dispensable for the development of local skin inflammation. Selective TLR7 triggering of Langerin(+) DCs resulted in attenuated disease, whereas their depletion did not alter the severity of skin lesions. Moreover, after IMQ-painting, IL-23 was exclusively produced by Langerin(neg) DCs in vivo. In conclusion, TLR7-activated Langerin(neg) cDCs trigger psoriatic plaque formation via IL-23-mediated activation of innate IL-17/IL-22-producing lymphocytes, independently of pDCs or IFN-I. These results suggest therapeutic targeting of IL-23 production by cDCs to refine current treatment strategies for psoriasis.

Increased accumulation of regulatory granulocytic myeloid cells in mannose receptor C type 1-deficient mice correlates with protection in a mouse model of neurocysticercosis.

Neurocysticercosis (NCC) is a central nervous system (CNS) infection caused by the metacestode stage of the parasite Taenia solium. During NCC, the parasites release immunodominant glycan antigens in the CNS environment, invoking immune responses. The majority of the associated pathogenesis is attributed to the immune response against the parasites. Glycans from a number of pathogens, including helminths, act as pathogen-associated molecular pattern molecules (PAMPs), which are recognized by pattern recognition receptors (PRRs) known as C-type lectin receptors (CLRs). Using a mouse model of NCC by infection with the related parasite Mesocestoides corti, we have investigated the role of mannose receptor C type 1 (MRC1), a CLR which recognizes high-mannose-containing glycan antigens. Here we show that MRC1(-/-) mice exhibit increased survival times after infection compared with their wild-type (WT) counterparts. The decreased disease severity correlates with reduced levels of expression of markers implicated in NCC pathology, such as interleukin-1ß (IL-1ß), IL-6, CCL5, and matrix metalloproteinase 9 (MMP9), in addition to induction of an important repair marker, fibroblast growth factor 2 (FGF2). Furthermore, the immune cell subsets that infiltrate the brain of MRC1(-/-) mice are dramatically altered and characterized by reduced numbers of T cells and the accumulation of granulocytic cells with an immune phenotype resembling granulocytic myeloid-dependent suppressor cells (gMDSCs). The results suggest that MRC1 plays a critical role in myeloid plasticity, which in turn affects the adaptive immune response and immunopathogenesis during murine NCC.

Displasia ectodérmica anhidrótica asociada a déficit de lectina de unión a manosa / Anhydrotic ectodermal dysplasia associated to mannose-binding lectin deficiency

La lectina de unión a la manosa (mannose-binding lectin [MBL]) es una proteína sérica perteneciente al sistema inmunitario innato. Se une a los azúcares de las membranas de múltiples microorganismos, favoreciendo su opsonización y eliminación. El déficit de MBL resulta del polimorfismo del gen MBL2 y se asocia a una amplia variedad de infecciones recurrentes, incluidas las infecciones del tracto respiratorio. Presentamos un caso de displasia ectodérmica anhidrótica asociada a un déficit de MBL, inmunodeficiencia nunca descrita en pacientes afectados de displasia ectodérmica anhidrótica(AU)

Mannose-binding lectin (MBL) is a serum protein of the innate immune system.MBL enhances opsonophagocytosis by binding to carbohydrates expressed by multiple pathogens.MBL deficiency is due to polymorphisms in the structural and promoter sequences of the MBL2 gene and is associated with variety of recurrent infections, including respiratory tract infections. We present a case of anhidrotic ectodermal dysplasia associated with severe mannose-binding lectin deficiency, never described in patients with anhidrotic ectodermal dysplasia(AU)

Mannose-binding lectin-associated serine protease-1 is a significant contributor to coagulation in a murine model of occlusive thrombosis.

Bleeding disorders and thrombotic complications constitute a major cause of death and disability worldwide. Although it is known that the complement and coagulation systems interact, no studies have investigated the specific role or mechanisms of lectin-mediated coagulation in vivo. FeCl(3) treatment resulted in intra-arterial occlusive thrombogenesis within 10 min in wild-type (WT) and C2/factor B-null mice. In contrast, mannose-binding lectin (MBL)-null and MBL-associated serine protease (MASP)-1/-3 knockout (KO) mice had significantly decreased FeCl(3)-induced thrombogenesis. Reconstitution with recombinant human (rh) MBL restored FeCl(3)-induced thrombogenesis in MBL-null mice to levels comparable to WT mice, suggesting a significant role of the MBL/MASP complex for in vivo coagulation. Additionally, whole blood aggregation demonstrated increased MBL/MASP complex-dependent platelet aggregation. In vitro, MBL/MASP complexes were captured on mannan-coated plates, and cleavage of a chromogenic thrombin substrate (S2238) was measured. We observed no significant differences in S2238 cleavage between WT, C2/factor B-null, MBL-A(-/-), or MBL-C(-/-) sera; however, MBL-null or MASP-1/-3 KO mouse sera demonstrated significantly decreased S2238 cleavage. rhMBL alone failed to cleave S2238, but cleavage was restored when rMASP-1 was added to either MASP-1/-3 KO sera or rhMBL. Taken together, these findings indicate that MBL/MASP complexes, and specifically MASP-1, play a key role in thrombus formation in vitro and in vivo.

Conditional deletion of TGF-ßR1 using Langerin-Cre mice results in Langerhans cell deficiency and reduced contact hypersensitivity.

The critical role of Langerhans cells (LC) in contact hypersensitivity (CHS) was recently questioned in studies using different LC-depletion mouse models. On one hand, inducible ablation of LC led to diminished ear swelling, suggesting functional redundancy between LC and (Langerin(+)) dermal dendritic cells (DC). On the other hand, constitutive or acute depletion of LC resulted in an enhanced reaction, supporting a regulatory role of LC in CHS. To address this controversy by conditional gene targeting, we generated Langerin-Cre knockin mice. Breeding these mice to a Cre-reporter strain demonstrated robust and specific DNA recombination in LC, as well as other Langerin(+) tissue DC. In agreement with the vital requirement of TGF-ß signaling for LC development, crossing Langerin-Cre to mice homozygous for a loxP-flanked TGF-ßR1 allele resulted in permanent LC deficiency, whereas the homeostasis of dermal Langerin(+) DC was unaffected. In the absence of LC, induction of CHS in these Langerin(+) DC-specific TGF-ßR1-deficient mice elicited decreased ear swelling compared with controls. This novel approach provided further evidence against a regulatory function of LC in CHS. Moreover, these Langerin-Cre mice represent a unique and powerful tool to dissect the role and molecular control of Langerin(+) DC populations beyond LC.

Mice deficient in LMAN1 exhibit FV and FVIII deficiencies and liver accumulation of α1-antitrypsin.

The type 1-transmembrane protein LMAN1 (ERGIC-53) forms a complex with the soluble protein MCFD2 and cycles between the endoplasmic reticulum (ER) and the ER-Golgi intermediate compartment (ERGIC). Mutations in either LMAN1 or MCFD2 cause the combined deficiency of factor V (FV) and factor VIII (FVIII; F5F8D), suggesting an ER-to-Golgi cargo receptor function for the LMAN1-MCFD2 complex. Here we report the analysis of LMAN1-deficient mice. Levels of plasma FV and FVIII, and platelet FV, are all reduced to ∼ 50% of wild-type in Lman1(-/-) mice, compared with the 5%-30% levels typically observed in human F5F8D patients. Despite previous reports identifying cathepsin C, cathepsin Z, and α1-antitrypsin as additional potential cargoes for LMAN1, no differences were observed between wild-type and Lman1(-/-) mice in the levels of cathepsin C and cathepsin Z in liver lysates or α1-antitrypsin levels in plasma. LMAN1 deficiency had no apparent effect on COPII-coated vesicle formation in an in vitro assay. However, the ER in Lman1(-/-) hepatocytes is slightly distended, with significant accumulation of α1-antitrypsin and GRP78. An unexpected, partially penetrant, perinatal lethality was observed for Lman1(-/-) mice, dependent on the specific inbred strain genetic background, suggesting a potential role for other, as yet unidentified LMAN1-dependent cargo proteins.

Design of neo-glycoconjugates that target the mannose receptor and enhance TLR-independent cross-presentation and Th1 polarization.

Cross-presentation is an important mechanism by which DCs present exogenous antigens on MHC-I molecules, and activate CD8(+) T cells, cells that are crucial for the elimination of tumors. We investigated the feasibility of exploiting the capacity of the mannose receptor (MR) to improve both cross-presentation of tumor antigens and Th polarization, processes that are pivotal for the anti-tumor potency of cytotoxic T cells. To this end, we selected two glycan ligands of the MR, 3-sulfo-Lewis(A) and tri-GlcNAc (N-acetylglucosamine), to conjugate to the model antigen OVA and assessed in vitro the effect on antigen presentation and Th differentiation. Our results demonstrate that conjugation of either 3-sulfo-Lewis(A) or tri-GlcNAc specifically directs antigen to the MR. Both neo-glycoconjugates showed, even at low doses, improved uptake as compared with native OVA, resulting in enhanced cross-presentation. Using MR(-/-) and MyD88-TRIFF(-/-) bone marrow-derived DCs (BMDCs), we show that the cross-presentation of the neo-glycoconjugates is dependent on MR and independent of TLR-mediated signaling. Whereas proliferation of antigen-specific CD4(+) T cells was unchanged, stimulation with neo-glycoconjugate-loaded DCs enhanced the generation of IFN-γ-producing T cells. We conclude that modification of antigen with either 3-sulfo-Lewis(A) or tri-GlcNAc enhances cross-presentation and permits Th1 skewing, through specific targeting of the MR, which may be beneficial for DC-based vaccination strategies to treat cancer.

Langerin+ dermal dendritic cells are critical for CD8+ T cell activation and IgH γ-1 class switching in response to gene gun vaccines.

The C-type lectin langerin/CD207 was originally discovered as a specific marker for epidermal Langerhans cells (LC). Recently, additional and distinct subsets of langerin(+) dendritic cells (DC) have been identified in lymph nodes and peripheral tissues of mice. Although the role of LC for immune activation or modulation is now being discussed controversially, other langerin(+) DC appear crucial for protective immunity in a growing set of infection and vaccination models. In knock-in mice that express the human diphtheria toxin receptor under control of the langerin promoter, injection of diphtheria toxin ablates LC for several weeks whereas other langerin(+) DC subsets are replenished within just a few days. Thus, by careful timing of diphtheria toxin injections selective states of deficiency in either LC only or all langerin(+) cells can be established. Taking advantage of this system, we found that, unlike selective LC deficiency, ablation of all langerin(+) DC abrogated the activation of IFN-γ-producing and cytolytic CD8(+) T cells after gene gun vaccination. Moreover, we identified migratory langerin(+) dermal DC as the subset that directly activated CD8(+) T cells in lymph nodes. Langerin(+) DC were also critical for IgG1 but not IgG2a Ab induction, suggesting differential polarization of CD4(+) T helper cells by langerin(+) or langerin-negative DC, respectively. In contrast, protein vaccines administered with various adjuvants induced IgG1 independently of langerin(+) DC. Taken together, these findings reflect a highly specialized division of labor between different DC subsets both with respect to Ag encounter as well as downstream processes of immune activation.