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HB8 is a new monoclonal antibody, prepared against human lymphocytes, which has been found to react with elastic fibres, possibly the microfibrillar component. Samples of normal human and animal skin and human skin from various pathological conditions were subjected to immunolabelling with HB8, and alternate sections from each sample were stained by a standard orcein procedure. The individual fibres were clearly marked by the HB8 and this was confirmed by comparison with the standard clastic tissue stain. HB8 provides a new direct, practical and accurate method for the study of elastic tissue. [ABSTRACT FROM AUTHOR]

Dendritic cells, a sentinel immunity cell lineage, include different cell subsets that express various C-type lectins. For example, epidermal Langerhans cells express langerin, and some dermal dendritic cells express DC-SIGN. Langerin is a crucial component of Birbeck granules, the Langerhans cell hallmark organelle, and may have a preventive role toward HIV, by its internalization into Birbeck granules. Since langerin carbohydrate recognition domain (CRD) is crucial for HIV interaction and Birbeck granule formation, we produced the CRD of human langerin and solved its structure at 1.5 A resolution. On this basis gp120 high-mannose oligosaccharide binding has been evaluated by molecular modeling. Hydrodynamic studies reveal a very elongated shape of recombinant langerin extracellular domain (ECD). A molecular model of the langerin ECD, integrating the CRD structure, has been generated and validated by comparison with hydrodynamic parameters. In parallel, Langerhans cells were isolated from human skin. From their analysis by electron microscopy and the langerin ECD model, an ultrastructural organization is proposed for Birbeck granules. To delineate the role of the different langerin domains in Birbeck granule formation, we generated truncated and mutated langerin constructs. After transfection into a fibroblastic cell line, we highlighted, in accordance with our model, the role of the CRD in the membrane zipping occurring in BG formation as well as some contribution of the cytoplasmic domain. Finally, we have shown that langerin ECD triggering with a specific mAb promotes global rearrangements of LC morphology. Our results open the way to the definition of a new membrane deformation mechanism.

Dendritic cells (DC) are the most potent antigen-presenting cells of the organism. They are specialized to capture, process, and present antigen via the MHC class II as well as the MHC class I pathways to CD4+ and CD8+ T cells, respectively. This results in T cell-mediated immune responses that are likely to counteract the generation and propagation of tumors in vivo. Therefore, we studied the distribution of dendritic cells in mammary Paget's disease. Paraffin-embedded samples of Paget's disease of the breast (n=27) and of disease-free epidermis of the nipple (n=10) were investigated immunohistochemically for the presence of dendritic cells, in particular of Langerhans cells, using antibodies against S-100, CD1a, and HLA-DR, as well as novel reagents against Langerin/CD207, DC-LAMP/CD208 and p55 (Fascin), the latter two being specific for mature dendritic cells. Paget samples presented a decrease of CD1a+, S-100+, and Langerin+ intraepidermal Langerhans cells in almost all cases. This was paralleled by a concentration of immature dendritic cells in the tumor-infiltrated tissue itself. Similar to infiltrating breast carcinoma we observed a marked increase of DC-LAMP+ and p55+ mature dendritic cells in the corial tissue beneath the tumor. These cells were almost always found in ribbon-like or nodular lymphocytic infiltrates. Moreover, rare mature dendritic cells were also found in the Paget cell-infiltrated epidermis of the nipple, i.e. in the tumorous lesion itself. These findings may indicate an effective ongoing anti-tumor immune response in this part of spreading breast cancer.

Langerin/CD207 is expressed by a subset of dendritic cells (DC), the epithelial Langerhans cells. However, langerin is also detected among lymphoid tissue DC. Here, we describe striking differences in langerin-expressing cells between inbred mouse strains. While langerin+ cells are observed in comparable numbers and with comparable phenotypes in the epidermis, two distinct DC subsets bear langerin in peripheral, skin-draining lymph nodes of BALB/c mice (CD11c(high) CD8alpha(high) and CD11c(low) CD8alpha(low)), whereas only the latter subset is present in C57BL/6 mice. The CD11c(high) subset is detected in mesenteric lymph nodes and spleen of BALB/c mice, but is virtually absent from C57BL/6 mice. Similar differences are observed in other mouse strains. CD11c(low) langerin+ cells represent skin-derived Langerhans cells, as demonstrated by their high expression of DEC-205/CD205, maturation markers, and recruitment to skin-draining lymph nodes upon imiquimod-induced inflammation. It will be of interest to determine the role of lymphoid tissue-resident compared to skin-derived langerin+ DC.

Dendritic cells (DCs) represent key professional antigen-presenting cells capable of initiating primary immune responses. A specialized subset of DCs, the Langerhans cells (LCs), are located in the stratified squamous epithelial layer of the skin and within the mucosal epithelial lining of the vaginal and oral cavities. The vaginal mucosa undergoes cyclic changes under the control of sex hormones, and the renewal characteristics of the vaginal epithelial DCs (VEDCs) remain unknown. Here, we examined the origin of VEDCs. In contrast to the skin epidermal LCs, the DCs in the epithelium of the vagina were found to be repopulated mainly by nonmonocyte bone-marrow-derived precursors, with a half-life of 13 days under steady-state conditions. Upon infection with HSV-2, the Gr-1(hi) monocytes were found to give rise to VEDCs. Furthermore, flow cytometric analysis of the VEDCs revealed the presence of at least three distinct populations, namely, CD11b(+)F4/80(hi), CD11b(+)F4/80(int), and CD11b(-)F4/80(-). Importantly, these VEDC populations expressed CD207 at low levels and had a constitutively more activated phenotype compared with the skin LCs. Collectively, our results revealed mucosa-specific features of the VEDCs with respect to their phenotype, activation status, and homeostatic renewal potential.

In this study we report the characterization of a population of lung resident CD11b(-)CD11c(+) cells that are able to take up inhaled antigen and retain it for extended periods of time. Ovalbumin conjugated to fluorescein-isothiocyanate (FITC-OVA) administered intranasally to mice was taken up by two main populations of cells in the lung, a migratory CD11c(+)CD11b(+) population consisting of dendritic cells (DC), which rapidly transported antigen to the draining lymph node (LN), and a resident CD11b(-)CD11c(+) population that retained engulfed antigen without apparently degrading it for up to 8 wk after administration. The FITC(+)CD11b(-)CD11c(+) cells did not migrate to draining LN at a detectable rate, and did not up-regulate expression of costimulatory molecules in response to LPS treatment. FITC(+)CD11b(-)CD11c(+) cells were found in the lung and bronchoalveolar lavage fluid, and their distribution was compatible with macrophages. Although FITC(+)CD11b(-)CD11c(+) cells expressed the DC marker DEC205 and other molecules associated with antigen-presenting cell function, they did not induce proliferation of antigen-specific CD4(+) T cells in vitro or acute cytokine production by activated CD4(+) T cells in vivo. Thus, FITC(+)CD11b(-)CD11c(+) cells appear to represent an intermediate cell type sharing properties with DC and macrophages. These cells may have a role in modulating the responses of lung resident T cells to inhaled antigens.

Epidermal Langerhans cells (LC) play a pivotal role in initiating and maintaining primary immune responses in the skin. In the present study, we asked whether peroxisome proliferator-activated receptor-alpha (PPARalpha) activation modulates LC function. Our results show that PPARalpha is expressed in immature LC and is down-regulated in mature LC suggesting that an early decrease of PPARalpha expression in LC may allow them to mature after contact with an Ag. We further show that pharmacologic PPARalpha activation inhibits LC maturation, migratory capacity, cytokine expression, and the ability to drive T cell proliferation. Moreover, PPARalpha activation inhibits NF-kappaB but not stress-activated protein kinase/JNK, p38MAPK, and ERK1/2. In conclusion, PPARalpha activation by endogenous ligands may provide a molecular signal that allows LC to remain in an immature state within the epidermis for extended periods of time despite minor environmental stimuli.

Although several studies have suggested relatively slow turnover of Langerhans cells (LCs), their actual lifespan remains elusive. Here we report the development of a new intravital imaging system for studying LC efflux and influx. Epidermal LCs expressing enhanced green fluorescent protein (EGFP) were visualized in anesthetized I-Abeta-EGFP knock-in mice by confocal microscopy. By overlaying two sets of EGFP+ LC images recorded in the same microscopic fields at time 0 and 24 hours later, we identified LC subpopulations that had disappeared from or newly emerged in the epidermis during that period. Of >10,000 LCs analyzed in this manner, an overwhelming majority (97.8+/-0.2%) of LCs showed no significant changes in the x-y locations, whereas 1.3+/-0.1% of the LCs that were found at time 0 became undetectable 24 hours later, representing LC efflux. Conversely, 0.9+/-0.1% of the LCs that were found at time 24 hours were not detectable at time 0, representing LC influx. From these frequencies, we estimated the half-life of epidermal LCs to range from 53 to 78 days, providing new insights into the immunobiology of LCs. Our intermittent imaging approach may be regarded as a technical breakthrough enabling direct visual assessment of LC turnover in living animals.

Objective: We investigated whether the expression of CD11b on precursors derived in vitro from CD34+ hematopoietic stem cells was related to their ability to generate CD11b- and CD11b+ Langerhans dendritic cells (LC)., Methods: Human CD34+ cells purified from cord blood were cultured with FLT3 ligand, thrombopoietin, and stem cell factor (FTS) for 2 weeks, analyzed, and sorted by FACS. Sorted fractions were cultured as above, or differentiated into LC with GM-CSF, IL-4, and TGF-beta1 (G4-TGF) for 6 days. The capacity of LC to internalize langerin and dextran was assessed., Results: Ex vivo, human CD34+ cells were CD11b- and mostly CLA+. After 2 weeks of culture with FTS, CD34- CLA- CD11b- and CD34- CLA- CD11b+ cells emerged. CD11b- cells were the most ancestral because they were the only ones to proliferate with FTS, and constantly generated CD11b+ cells. Both CD11b- and CD11b+ sorted cells generated E-cadherin+ langerin+ LC after incubation with G4-TGF. The former fraction contained 46% +/- 15% of E-cadherin+ and 10% +/- 5% of langerin+ cells, whereas in the latter fraction these values reached respectively 66% +/- 23% and 30% +/- 16% (mean +/- SD, n = 7, p < 0.056). Looking at functional properties, CD11b- and CD11b+ LC were similar in terms of langerin and dextran endocytosis. By contrast, only CD11b+ LC internalized fluorescent LPS., Conclusion: Human CD34+ CD11b- cells differentiate in FTS culture into a CD34- CD11b- precursor that in turn generates CD34- CD11b+ cells. These cells are enriched in LC precursors compared to CD34- CD11b- cells. Both CD11b- and CD11b+ LC are generated in vitro, and each fraction may assume different functions in inflammatory situations.

Langerhans cells have been thought to play a major role as APCs for induction of specific immune responses to Leishmania major. Although their requirement for control of infection has been challenged recently, it remains unclear whether they can transport Ag to lymph nodes and promote initiation of T cell responses. Moreover, the role of dermal dendritic cells (DCs), another population of skin DCs, has so far not been addressed. We have investigated the origin and characterized the cell population responsible for initial activation of L. major-specific T cells in susceptible and resistant mice. We found that Ag presentation in draining lymph nodes peaks as early as 24 h after infection and is mainly mediated by a population of CD11c(high)CD11b(high)Gr-1-CD8-langerin- DCs residing in lymph nodes and acquiring soluble Ags possibly drained through the conduit network. In contrast, skin-derived DCs, including Langerhans cells and dermal DCs, migrated poorly to lymph nodes and played a minor role in early T cell activation. Furthermore, prevention of migration through early removal of the infection site did not affect Ag presentation by CD11c(high) CD11b(high) DCs and activation of Leishmania major-specific naive CD4+ T cells in vivo.