Langerhans Cells In Lymph Nodes Research Articles

EpCAM expressed by epidermal langerhans cells modulates immunization to an epicutaneously-applied protein antigen

Langerhans cells (LC) are required for efficient formation of Type 2 (IgG1 and IgE) Ab in response to foreign proteins that are applied to skin without adjuvant. Immunization is mediated via LC that extend dendrites through tight junctions (TJ) to acquire topically applied Ag and subsequently migrate to regional lymph nodes (LN). EpCAM (CD326) is expressed at high levels by LC. We previously reported that EpCAM promotes LC dendrite mobility, as well as LC migration within epidermis and from epidermis to regional LN in response to contact sensitizers. We also demonstrated that, in intestinal epithelial cells, EpCAM regulates the levels of expression and distribution of selected claudins. We hypothesized that in the absence of EpCAM, acquisition of Ag by LC might be impaired and topical immunization to proteins might be reduced. To test this, we studied conditional KO mice with EpCAM-deficient LC (cKO mice). Control (WT) and cKO LC dendrites docked with and penetrated the epidermal TJ with equal efficiencies. LC from both strains internalized surface biotinylated self-proteins. Unexpectedly, topical immunization of cKO mice with ovalbumin (Ova) led to the accumulation of increased numbers of LC in regional LN. This was accompanied by enhanced proliferation of adoptively transferred Ova- reactive OT-II cells and enhanced formation of Ova-specific Ab in cKO mice. These results indicate that EpCAM regulates topical immunization to protein acting via LC, but immunization is potentiated by EpCAM deficiency rather than inhibited. We propose that EpCAM-dependent mechanisms that regulate LC migration may differ in the setting of limited inflammation associated with topical immunization with protein as compared with the intense inflammation triggered by strong contact sensitizers.

EpCAM Expressed by Murine Epidermal Langerhans Cells Modulates Immunization to an Epicutaneously Applied Protein Antigen

Langerhans cells (LCs) induce type 2 antibodies reactive with protein antigens that are applied to murine skin in the absence of adjuvant after extending their dendrites through tight junctions to acquire antigens and migrating to regional lymph nodes. In response to contact sensitizers, epithelial cell adhesion molecule (EpCAM) on LCs promotes LC dendrite mobility and LC migration. In epithelial cells, EpCAM regulates expression and distribution of selected tight junctions-associated claudins. To determine if EpCAM regulates claudins in LC and immune responses to externally applied proteins, we studied conditional knockout mice with EpCAM-deficient LCs. Although LC claudin-1 levels were dramatically reduced in the absence of EpCAM, conditional knockout mice with EpCAM-deficient LCs and control LC dendrites docked with epidermal tight junctions with equal efficiencies and ingested surface proteins. Topical immunization of conditional knockout mice with EpCAM-deficient LCs with ovalbumin led to increased induction of type 2 Ova-specific antibodies and enhanced proliferation of ovalbumin-reactive T cells associated with increased accumulation of LCs in lymph nodes. These results suggest that, in the absence of strong adjuvants, EpCAM-deficient LCs exhibit increased migration to regional lymph nodes. EpCAM appears to differentially regulate LC mobility/migration inthe setting of limited inflammation as compared with the intense inflammation triggered by contact sensitizers.

Arsenic mobilizes Langerhans cell migration and induces Th1 response in epicutaneous protein sensitization via CCL21: A plausible cause of decreased Langerhans cells in arsenic-induced intraepithelial carcinoma

Arsenic, still a significant environmental threat in several regions in the world, induces various cancers, including lungs, skin, and bladder. Arsenic-induced Bowen's disease (As-BD) is generally an indolent cutaneous intraepithelial carcinoma in susceptible people. Patients with As-BD have been found to have attenuated contact hypersensitivity. Skin samples collected from these patients have reduced numbers of Langerhans cells (LCs), the major epidermal antigen presenting cells expressing Langerins. This study uses an epicutaneous protein sensitization model to investigate the mechanism through which LCs are decreased in As-BD. It further investigates the possibility that arsenic alters LC migration and polarizes Th responses. To do this, we patch-sensitized Balb/c mice or DT-treated Langerin-DTR mice (conditional depletion of Langerin+ cells) with OVA or PBS, and fed them water containing 300ppb arsenic or regular water for 200μl for five days. Ninety-six hours after OVA sensitization, Langerin+EpCAM+ cells in arsenic-treated WT mice were significantly increased in draining lymph nodes and decreased in epidermis without changes in the dermis. Lymph node cells from arsenic-treated WT mice were found to proliferate more than lymph node cells from control PBS-treated mice after OVA challenge in vitro. They also secreted more IFN-γ and IL-12, but not IL-4, IL-13, or IL-17. However, cell proliferation and the induction of IFN-γ by arsenic were found to be abolished in DT-treated Langerin-DTR mice. The expressions of CCL21 and CXCL12 were also increased in lymph nodes from arsenic-treated WT mice. The administration of a neutralizing antibody against CCL21, but not CXCL12, abolished the increase of LCs in lymph nodes in vivo. The results of this study, the first to study oral arsenic polarization of Th1 responses in epicutaneous protein sensitization through CCL21-mediated LC migration, suggest the chronicity of As-BD without invasion might result from enhanced Th1 responses and altered LC migrations by arsenic.

Arsenic enhances Langerhans cell migration to draining lymph nodes via CCL21 and IFN-γproduction in a model of epicutaneous protein sensitization (89.19)

Abstract Arsenic induces multiple Bowen's disease (As-BD), or cutaneous carcinoma in situ, that runs an indolent course. Immune responses are important modifiers for the development of As-BD. We have previously reported that Langerhans cells (LCs) were reduced in As-BD, but how arsenic alters LC migration and polarizes Th responses remains unknown. Using an epicutaneous protein sensitization model, Balb/c mice were patch-sensitized with OVA and received feeding of 300 ppm arsenic or PBS for 200ul for 5 days. Defined as CD207+MHCII+ cells, the number of LCs was significantly decreased in patched epidermis, but increased in draining lymph nodes, with no changes in dermis and spleens 96 hours after OVA sensitization in arsenic-treated mice. There was a parallel increase of CCL21 in lymph nodes from arsenic-treated mice, and enhanced cellular proliferation and IFN-γ secretion in vitro were also noted in lymph node cells from arsenic-treated mice. Notably, in vivo administration of a neutralizing antibody against CCL21 abolished the increase of LCs in lymph nodes. These results suggest, therefore, that in this model, arsenic exposure enhanced LC migration to draining lymph nodes via CCL21 and interferon-γ production, and that chronic nature of As-BD might result from enhanced Th1 responses and LC migration.

Complete donor chimaerism of Langerhans cells in lymph node early after allogeneic bone marrow transplantation

Host-derived Langerhans cells (LCs) are crucial antigen-presenting cells that cause graft-vs.-host disease after allogeneic haematopoietic stem cell transplantation (HSCT). However, chimaerism of LCs after allogeneic HSCT is largely unknown in humans. We here report a case that developed dermatopathic lymphadenitis accompanied by an accumulation of donor-derived LCs in the second month after allogeneic HSCT with reduced-intensity conditioning. This is the first case to show that donor LCs have the ability to migrate into draining lymph nodes and replace host LCs early after HSCT in humans.

Visualization and Characterization of Migratory Langerhans Cells in Murine Skin and Lymph Nodes by Antibodies Against Langerin/CD207

Dendritic cells are professional antigen-presenting cells that initiate primary immunity. Migration from sites of antigen uptake to lymphoid organs is crucial for the generation of immune responses. We investigated the migratory pathways specifically of epidermal Langerhans cells by tracing them from the epidermis to the draining lymph nodes. This was possible with a new monoclonal antibody, directed against murine Langerin/CD207, a type II lectin specific for Langerhans cells. In situ, resident, and activated Langerhans cells express Langerin in the epidermis and on their way through dermal lymphatic vessels. Both emigrated and trypsinization-derived Langerhans cells expressed high levels of Langerin intracellularly but reduced it upon prolonged culture periods. Sizeable numbers of Langerin+ cells were found in skin draining lymph nodes but not in mesenteric nodes. Langerin+ cells localized to the T cells areas and rarely to B cell zones. Numbers of Langerin-expressing cells increased after application of a contact sensitizer. In the steady state, Langerhans cells in the skin-draining nodes expressed maturation markers, such as 2A1 and costimulatory molecules CD86 and CD40. These molecules, CD86 and CD40, were further upregulated upon inflammatory stimuli such as contact sensitization. Thus, the novel anti-Langerin monoclonal antibody permits the unequivocal visualization of migratory Langerhans cells in the lymph nodes for the first time and thereby allows to dissect the relative immunogenic or tolerogenic contributions of Langerhans cells and other types of dendritic cells.

Contribution of Langerhans cell-derived IL-18 to contact hypersensitivity.

The epidermal Langerhans cells (LC), a member of the dendritic cell family, and the LC-derived cytokine IL-12 play a pivotal role in the initiation of contact hypersensitivity (CHS), a Th1 immune response in the skin. Because IL-18, another LC-derived cytokine, shares functional and biological properties with IL-12, we examined a potential role for IL-18 in CHS initiation. Our studies demonstrated that during the induction phase of murine CHS, IL-18 mRNA was significantly up-regulated in the skin-draining lymph nodes (LN). Migratory hapten-modified LC in LN expressed high levels of IL-18 mRNA and secreted functional IL-18 protein. LN cells produced significant amounts of IFN-gamma following in vitro IL-12 stimulation, which could be partially blocked by anti-IL-18 Ab, suggesting a synergistic role for endogenous IL-18 in IFN-gamma production by LN cells. Because mature IL-18 requires cleavage of immature precursors by caspase-1, we further examined IL-12-induced IFN-gamma production in caspase-1(-/-) LN cells. An impaired IFN-gamma production was seen in caspase-1(-/-) LN cells, which could be restored by addition of exogenous IL-18, supporting a role for caspase-1-cleaved, mature IL-18 in IFN-gamma production. Finally, in vivo studies showed that CHS responses were significantly inhibited in mice treated with neutralizing IL-18 Ab as well as in caspase-1(-/-) mice deficient in mature IL-18, indicating functional relevance for IL-18 in CHS. Taken together, our studies demonstrate that LC-derived IL-18 significantly contributes to CHS initiation.

High incidence of Langerhans cells in lymph nodes of athymic nude mice: an ultrastructural and morphometric study.

Cervical and axillary lymph nodes of athymic nude mice were compared morphometrically and ultrastructurally with those of normal littermates. The lymph nodes of the nude mice were larger and the volumes of the follicle, paracortex, and medulla of the lymph nodes were all larger. The paracortex of nude mice had few lymphocytes and a large number of interdigitating cells (IDC) and Langerhans cells (Lc). The results suggest that the high incidence of Lc and IDC in the lymph nodes of nude mice is due to cell accumulation and not lymphocyte depletion.

Langerhans cells: Target cells in immune complex reactions

Skin of normal, cobra venom extract-treated, and C 4-deficient guinea pigs was injected with ferritin-antiferritin or with peroxidase-antiperoxidase immune complexes. Skin and draining lymph nodes were studied to compare the phagocytosis of these immune complexes by Langerhans cells (LC) and by macrophages. When complement was present, immune complexes were damaging to LC, and uptake of the immune complexes, although present, was limited. When components of complement were absent or diminished, increased numbers of LC in lymph nodes were seen, but damage to LC was absent or decreased. However no detectable change in the amount of phagocytosis by LC was noted. Since some LC can carry antigen from skin to lymph nodes and may be involved in the presentation of antigen to lymphoid cells in some cell-mediated immune responses, impairment or abolition of LC function by immune complexes could represent a mechanism through which the local presence of antibodies might interfere with the induction and elicitation of cellular immunity by antigen. Moreover, damage to LC and subsequent release of intracellular (lysosomal?) substances may constitute a general mechanism of response in the skin to injury and may be an integral part of inflammatory and allergic skin reactions.