Three-dimensional appearance of Langerhans cells in human gingival epithelium as revealed by confocal laser scanning microscopy

Human cytomegalovirus tropism for mucosal myeloid dendritic cells

Human CMV infections are a serious source of morbidity and mortality for immunocompromised patients and for the developing fetus. Because of this, the development of new strategies to prevent CMV acquisition and transmission is a top priority. Myeloid dendritic cells (DC) residing in the oral and nasal mucosae are among the first immune cells to encounter CMV during entry and greatly contribute to virus dissemination, reactivation from latency, and horizontal spread. Albeit affected by the immunoevasive tactics of CMV, mucosal DC remain potent inducers of cellular and humoral immune responses against this virus. Their natural functions could thus be exploited to generate long-lasting protective immunity against CMV by vaccination via the oronasal mucosae. Although related, epithelial Langerhans-type DC and dermal monocyte-derived DC interact with CMV in dramatically different ways. Whereas immature monocyte-derived DC are fully permissive to infection, for instance, immature Langerhans-type DC are completely resistant. Understanding these differences is essential to design innovative vaccines and new antiviral compounds to protect these cells from CMV infection in vivo.

Dendritic cells of the oral mucosa

The oral cavity contains distinct mucosal surfaces, each with its own unique distribution of dendritic cell (DC) subsets. In addition to tissue-specific properties, such organization might confer differential immune outcomes guided by tissue-resident DCs, which translate in the lymph node into an overall immune response. This process is further complicated by continual exposure and colonization of the oral cavity with enormous numbers of diverse microbes, some of which might induce destructive immunity. As a central cell type constantly monitoring changes in oral microbiota and orchestrating T-cell function, oral DCs are of major importance in deciding whether to induce immunity or tolerance. In this review, an overview of the phenotype and distribution of DCs in the oral mucosa is provided. In addition, the role of the various oral DC subsets in inducing immunity vs. tolerance, as well as their involvement in several oral pathologies is discussed.

Langerhans cells and their role in oral mucosal diseases

Dendritic cells are arguably the most potent antigen-presenting cells and may be the only cells capable of initiating the adaptive immune response. The epithelial residents of dendritic cells are Langerhans cells, which serve as the "sentinels" of the mucosa, altering the immune system not only to pathogen entry but also of tolerance to self antigen and commensal microbes. Oral mucosal Langerhans cells are capable of engaging and internalizing a wide variety of pathogens and have been found responsive to nickel in patients with nickel allergies, oral Candida species, oral lichen planus, lichenoid drug eruptions, graft versus host diseases, periodontal diseases median rhomboid glossitis, human immunodeficiency virus infection, hairy leukoplakia of the tongue, and oral squamous cell carcinoma. Review focuses on the role of antigen-presenting cells in particular Langerhans cells to better understand the mechanisms underlying immune responses. In this review, comprehensive detail about mucosal diseases has been compiled using the PubMed database and through textbooks.

Salivary defense proteins: their network and role in innate and acquired oral immunity

There are numerous defense proteins present in the saliva. Although some of these molecules are present in rather low concentrations, their effects are additive and/or synergistic, resulting in an efficient molecular defense network of the oral cavity. Moreover, local concentrations of these proteins near the mucosal surfaces (mucosal transudate), periodontal sulcus (gingival crevicular fluid) and oral wounds and ulcers (transudate) may be much greater, and in many cases reinforced by immune and/or inflammatory reactions of the oral mucosa. Some defense proteins, like salivary immunoglobulins and salivary chaperokine HSP70/HSPAs (70 kDa heat shock proteins), are involved in both innate and acquired immunity. Cationic peptides and other defense proteins like lysozyme, bactericidal/permeability increasing protein (BPI), BPI-like proteins, PLUNC (palate lung and nasal epithelial clone) proteins, salivary amylase, cystatins, prolin-rich proteins, mucins, peroxidases, statherin and others are primarily responsible for innate immunity. In this paper, this complex system and function of the salivary defense proteins will be reviewed.

Expression of heat shock proteins, Hsp70 and Hsp25, in the rat gingiva after irradiation with a CO2 laser in coagulation mode

BACKGROUND AND OBJECTIVE

The therapeutic rationale of low-energy pulsed CO(2) laser coagulation mode has not been clarified yet. We conducted this study to characterize the effect of low-energy pulsed CO(2) laser coagulation mode irradiation of the rat gingiva in terms of the expression of heat shock proteins.

MATERIAL AND METHODS

Laser irradiation was achieved with the parameters of 5 W, 600 mus pulse duration, and fluence of 326 J/cm(2). The gingiva dissected at different times after irradiation was processed for immunohistochemical examination of the expression of the heat shock proteins, Hsp70 and Hsp25.

RESULTS

One hour after irradiation, the epithelial keratinocytes facing the laser wound exhibited an overexpression of Hsp70 in their nucleus. The connective tissue cells facing the laser wound, which included fibroblasts and capillary endothelial cells, showed de novo expression of Hsp70 at 3 h post-irradiation, the level of which peaked at 1 d and thereafter decreased. An enhanced and/or de novo expression of Hsp25 in the connective tissue cells facing the laser wound became evident at 3 h after irradiation, and after 1 d the Hsp25-expressing cells increased in number and spread over the wound as wound repair progressed. There was a temporospatial difference in the expression pattern between Hsp70 and Hsp25, with only a few cells appearing to co-express both heat shock proteins.

CONCLUSION

The CO(2) laser treatment in coagulation mode produced the expression of heat shock proteins, and the findings suggest that while Hsp70 mainly conferred cell protection, Hsp25 was involved in the progress of wound repair as well as cell protection.

Dendritic cells at the oral mucosal interface

The mucosal lining of the respiratory and digestive systems contains the largest and most complex immune system in the body, but surprisingly little is known of the immune system that serves the oral mucosa. This review focuses on dendritic cells, particularly powerful arbiters of immunity, in response to antigens of microbial or tumor origin, but also of tolerance to self-antigens and commensal microbes. Although first discovered in 1868, the epidermal dendritic Langerhans cells remained enigmatic for over a century, until they were identified as the most peripheral outpost of the immune system. Investigators' ability to isolate, enrich, and culture dendritic cells has led to an explosion in the field. Presented herein is a review of dendritic cell history, ontogeny, function, and phenotype, and the role of different dendritic cell subsets in the oral mucosa and its diseases. Particular emphasis is placed on the mechanisms of recognition and capture of microbes by dendritic cells. Also emphasized is how dendritic cells may regulate immunity/tolerance in response to oral microbes.

Femtosecond two-photon high-resolution 3D imaging, spatial-volume rendering and microspectral characterization of immunolocalized MHC-II and mLangerin/CD207 antigens in the mouse epidermis

Langerhans cells (LCs) play a sentinel role by initiating both adaptive and innate immune responses to antigens pertinent to the skin. With the discovery of various LCs markers including antibodies to major histocompatibility complex class II (MHC-II) molecules and CD1a, intracellular presence of racket-shaped "Birbeck granules," and very recently Langerin/CD207, LCs can be readily distinguished from other subsets of dendritic cells. Femtosecond two-photon laser scanning microscopy (TPLSM) in recent years has emerged as an alternative to the single photon-excitation based confocal laser scanning microscope (CLSM), particularly for minimally-invasive deep-tissue 3D and 4D vital as well as nonvital biomedical imaging. We have recently combined high resolution two-photon immunofluorescence (using anti MHC-II and Langerin/CD207 antibodies) imaging with microspectroscopy and advanced image-processing/volume-rendering modalities. In this work, we demonstrate the use of this novel state-of-the-art combinational approach to characterize the steady state 3D organization and spectral features of the mouse epidermis, particularly to identify the spatial distribution of LCs. Our findings provide unequivocal direct evidence that, in the mouse epidermis, the MHC-II and mLangerin/CD207 antigens do indeed manifest a high degree of colocalization around the nucleus of the LCs, while in the distal dendritic processes, mLangerin/CD207 antigens are rather sparsely distributed as punctuate structures. This unique possibility to simultaneously visualize high resolution 3D-resolved spatial distributions of two different immuno-reactive antigens, namely MHC-II and mLangerin/CD207, along with the nuclei of LCs and the adjacent epidermal cells can find interesting applications. These could involve aspects associated with pragmatic analysis of the kinetics of LCs migration as a function of immuno-dermatological responses during (1) human Immunodeficiency virus disease progression, (2) vaccination and targeted gene therapy, (3) skin transplantation/plastic surgery, (4) ultraviolet and other radiation exposure, (5) tissue-engineering of 3D skin constructs, as well as in (6) cosmetic industry, to unravel the influence of cosmeceuticals.

Multiphoton high-resolution 3D imaging of Langerhans cells and keratinocytes in the mouse skin model adopted for epidermal powdered immunization

Langerhans cells (LCs) can be targeted with DNA-coated gold micro-projectiles ("Gene Gun") to induce potent cellular and humoral immune responses. It is likely that the relative volumetric distribution of LCs and keratinocytes within the epidermis impacts on the efficacy of Gene Gun immunization protocols. This study quantified the three-dimensional (3D) distribution of LCs and keratinocytes in the mouse skin model with a near-infrared multiphoton laser-scanning microscope (NIR-MPLSM). Stratum corneum (SC) and viable epidermal thickness measured with MPLSM was found in close agreement with conventional histology. LCs were located in the vertical plane at a mean depth of 14.9 microm, less than 3 mum above the dermo-epidermal boundary and with a normal histogram distribution. This likely corresponds to the fact that LCs reside in the suprabasal layer (stratum germinativum). The nuclear volume of keratinocytes was found to be approximately 1.4 times larger than that of resident LCs (88.6 microm3). Importantly, the ratio of LCs to keratinocytes in mouse ear skin (1:15) is more than three times higher than that reported for human breast skin (1:53). Accordingly, cross-presentation may be more significant in clinical Gene Gun applications than in pre-clinical mouse studies. These interspecies differences should be considered in pre-clinical trials using mouse models.