Langerhans cells (LCs) are prominent dendritic cells (DCs) in epithelia, but their role in immunity is poorly defined. To track and discriminate LCs from dermal DCs in vivo, we developed knockin mice expressing enhanced green fluorescent protein (EGFP) under the control of the langerin (CD207) gene. By using vital imaging, we showed that most EGFP(+) LCs were sessile under steady-state conditions, whereas skin inflammation induced LC motility and emigration to lymph nodes (LNs). After skin immunization, dermal DCs arrived in LNs first and colonized areas distinct from slower migrating LCs. LCs reaching LNs under steady-state or inflammatory conditions expressed similar levels of costimulatory molecules. Langerin and EGFP were also expressed on thymic DCs and on blood-derived, CD8alpha(+) DCs from all secondary lymphoid organs. By using a similar knockin strategy involving a diphtheria toxin receptor (DTR) fused to EGFP, we demonstrated that LCs were dispensable for triggering hapten-specific T cell effectors through skin immunization.

Langerhans cells (LC) are dendritic cells of the epidermis. They are highly specialized leukocytes that serve immunogenic and tolerogenic purposes. Here, we review some aspects of LC biology, emphasizing those areas where LC are or may turn out to be special.

cross-presentation ͉ dendritic cells ͉ epidermis ͉ mouse or murine ͉ epicutaneous

Antigen-presenting cells can capture antigens that are deposited in the skin, including vaccines given subcutaneously. These include different dendritic cells (DC) such as epidermal Langerhans cells (LC), dermal DC and dermal langerin+ DC. To evaluate access of dermal antigens to skin DC, we used mAb to two C-type lectin endocytic receptors, DEC-205/CD205 and langerin/CD207. When applied to murine and human skin explant cultures, these mAb were efficiently taken up by epidermal LC. Additionally, anti-DEC-205 targeted langerin+ CD103+ and langerin− CD103− mouse dermal DC. Unexpectedly, intradermal injection of either mAb, but not isotype control, resulted in strong and rapid labelling of LC in situ, implying that large molecules can diffuse through the basement membrane into the epidermis. Epidermal LC targeted in vivo by ovalbumin-coupled anti-DEC-205 potently presented antigen to CD4+ and CD8+ T cells. Thus, epidermal LC play a major role in uptake of lectin-binding ligands under standard vaccination conditions.

Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionThe reversal of immune tolerance represents one central goal in cancer immune therapies and serves as a rationale for developing [3,5]. Furthermore, these drugs can enhance the immunogenicity of the tumor epithelium, and as well change the immunosuppressive cytokine milieu produced by the tumor and its microenvironment, thereby facilitating the maturation and function of effector cells in innate and adaptive immunity [6]. The immunomodulatory effects of established anticancer drugs are also exploited to improve tumor vaccination protocols. An important animal model used in these studies is FVB/ N-MMTV-neu transgenic mice developing mammary cancer due to overexpression of neu, the normal rat homologue of HER2/erbB2 in the mammary gland [7]. These mice are immunotolerant to neu [8,9], but can be vaccinated with neu-directed vaccines to prevent tumor formation in combination with appropriate adjuvants such as GM-CSF, IL-12, and cyclophosphamide [10,11]. The IFN-induced transcription factor Stat1 has been described as important mediator of the antitumor response [12]. As a key regulator of innate as well as adaptive immunity, Stat1 is involved in immune surveillance [13] but has also been postulated to act as a tumor suppressor by tumor epithelium intrinsic mechanisms. As has been shown recently, Stat1-deficient mice spontaneously develop mammary tumors [14,15]. In MMTV-neu mammary tumor mice, deletion of Stat1 in the tumor epithelium as well as in the tumor stroma was shown to contribute to accelerated tumorigenesis [16,17]. The aim of the present study was to investigate this issue further in MMTV-neu mice as an animal model for erbB2-positive breast cancer, treated in vivo with two different types of drugs, the dual tyrosine kinase inhibitor lapatini which targets HER2/erbB2/neu and EGFR/erbB1, and the genotoxic anthracycline drug doxorubicin.Here, we show that in MMTV-neu mice the in vivo efficacy of lapatinib and/or doxorubicin treatment is dependent on CD8 . Both Stat1-deficient and -proficient mice developed mammary tumors with no significant differences in expression levels for erbB2 and in tumor histology ( Fig. 1A and Supporting Information Fig. 1).As described previously for other mouse models of erbB2-positive breast cancer [16,17], Stat1 deficiency resulted in a slight acceleration of the development of palpable tumors. Furthermore, we observed an increase in tumor multiplicity, with lowered levels of caspase 3 cleavage in the tumor and a slight increase of the fraction of proliferating cells in the tumor (Supporting Information Fig. 1). To assess the role of Stat1 in the response to chemotherapy, mice were treated with the erbB1/erbB2 targeting drug lapatinib and/or the genotoxic agent doxorubicin as soon as tumors were palpable. The response to therapy was monitored for 6 weeks. Treatment of Stat1-proficient mice either with lapatinib alone, doxorubicin or drug combination resu...

A role for Langerhans cells (LC) in the induction of immune responses in the skin has yet to be conclusively demonstrated. We used skin immunization with OVA protein to induce immune responses against OVA-expressing melanoma cells. Mice injected with OVA-specific CD8+ T cells and immunized with OVA onto barrier-disrupted skin had increased numbers of CD8+ T cells in the blood that produced IFN-γ and killed target cells. These mice generated accelerated cytotoxic responses after secondary immunization with OVA. Prophylactic or therapeutic immunization with OVA onto barrier-disrupted skin inhibited the growth of B16.OVA tumors. LC played a critical role in the immunization process because depletion of LC at the time of skin immunization dramatically reduced the tumor-protective effect. The topically applied Ag was presented by skin-derived LC in draining lymph nodes to CD8+ T cells. Thus, targeting of tumor Ags to LC in vivo is an effective strategy for tumor immunotherapy.

Vaccinations in medicine are typically administered into the muscle beneath the skin or into the subcutaneous fat. As a consequence, the vaccine is immunologically processed by antigenpresenting cells of the skin or the muscle. Recent evidence suggests that the clinically seldom used intradermal route is effective and possibly even superior to the conventional subcutaneous or intramuscular route. Several types of professional antigen-presenting cells inhabit the healthy skin. Epidermal Langerhans cells (CD207/langerin + ), dermal langerin neg , and dermal langerin + dendritic cells (DC) have been described, the latter subset so far only in mouse skin. In human skin langerin neg dermal DC can be further classified based on their reciprocal expression of CD1a and CD14. The relative contributions of these subsets to the generation of immunity or tolerance are still unclear. Yet, specializations of these different populations have become apparent. Langerhans cells in human skin appear to be specialized for induction of cytotoxic T lymphocytes; human CD14 + dermal DC can promote antibody production by B cells. It is currently attempted to rationally devise and improve vaccines by harnessing such specific properties of skin DC. This © Springer-Verlag Berlin Heidelberg 2011 nikolaus.romani@i-med.ac.at. Europe PMC Funders GroupAuthor Manuscript Curr Top Microbiol Immunol. Author manuscript; available in PMC 2015 January 07. Published in final edited form as:Curr Top Microbiol Immunol. 2012 ; 351: 113-138. doi:10.1007/82_2010_118. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts could be achieved by specifically targeting functionally diverse skin DC subsets. We discuss here advances in our knowledge on the immunological properties of skin DC and strategies to significantly improve the outcome of vaccinations by applying this knowledge. Modern Vaccine Science-Devising Rational VaccinesVaccinations in medicine are a success story. They are well established and well investigated. The traditional vaccines induce robust immunity against bacterial and viral microbes, thereby preventing the outbreak of infectious diseases. The commonly applied vaccines, which are used worldwide, were developed by microbiologists. Louis Pasteur discovered that distinct microbes cause diseases and that attenuated microbes can induce long-lived protection against a subsequent infection by the pathogenic, i.e., non-attenuated form of that organism. This was long before there was any clear understanding of cellular, let alone molecular mechanisms of vaccine immunity, such as the decisive role that dendritic cells (DC) have in this process (Steinman 2008b). The twentieth century brought major advances in our knowledge and understanding of the immune system. This initiated a new period of vaccine research that is based on our understanding and exploitation of key immune principles rather than on the empirical approach. A vaccine can be defined as a formulation that induces specific, non-toxic, and long-lasting immune...

Langerin/CD207 is a C-type lectin associated with formation of Birbeck granules (BG) in Langerhans cells (LC). Here, we describe a monoclonal antibody (mAb 205C1) recognizing the extracellular domain of mouse langerin. Cell-surface langerin was detected in all epidermal LC, which presented a uniform phenotype. Two subpopulations of langerin+ cells were identified in peripheral lymph nodes (LN). One population (subset 1) was CD11c(low/+)/CD8alpha(-/low)/CD11b+/CD40+/CD86+. The other population (subset 2) was CD11c(high)/CD8alpha+/CD11b(low), and lacked CD40 and CD86. Only subset 1 was fluorescein 5-isothiocyanate (FITC+) following painting onto epidermis, and the appearance of such FITC+ cells in draining LN was inhibited by pertussis toxin. Mesenteric LN, spleen, and thymus contained only a single population of langerin+ DC, corresponding to peripheral LN subset 2. Unexpectedly, BG were absent from spleen CD8alpha+ DC despite expression of langerin, and these organelles were not induced by mAb 205C1. Collectively, we demonstrate that two langerin+ DC populations (subsets 1 and 2) co-exist in mouse lymphoid tissue. Subset 1 unequivocally identifies epidermal LC-derived DC. The distribution of subset 2 indicates a non-LC origin of these langerin+ cells. These findings should facilitate our understanding of the role played by langerin in lymphoid organ DC subsets.