Oral mucosal Langerhans' cells

Relation of Langerhans cell size to buccal carcinoma

Oral cancer decreases quality of life despite timely medical management. The carcinogens in tobacco products and their role in tumorigenesis are well documented. Langerhans cells (LCs) are a subset of antigen-presenting cells (APCs) that monitor the tumor microenvironment and engulf carcinogens and foreign bodies. We investigated the distribution and size of LCs and their relation to the mode of tobacco consumption and clinical outcome in patients with buccal carcinoma. We recruited patients with oral cancer who were scheduled for tumor excision and men with urethral stricture undergoing substitution urethroplasty using buccal mucosa. Normal and tumor-adjacent tissues were stained with CD1a antibody. The distribution and mean diameter of 100 LCs/patient were determined. We found significantly smaller LCs in patients who chewed only tobacco compared to those who consumed tobacco by other means. The size of LCs decreased significantly with progressive stages of malignant disease. We found that patients with larger LCs survived longer than those with smaller LCs during an average follow-up of 24 months. We suggest a relation between the size of LCs and clinical outcomes in patients with buccal carcinoma.

Langerhans cell expression in oral submucous fibrosis: An immunohistochemical analysis

Introduction

Langerhans cells (LCs) are dendritic cells (DCs) of the epithelium which play a role in an array of oral lesions from gingivitis to oral cancer. Oral submucous fibrosis (OSMF), a potentially malignant disorder (PMD), is an insidious chronic disease with juxta-epithelial inflammatory changes leading to fibrosis. LCs may play a part in the ongoing inflammatory dysregulation of OSMF.

Objective

The study was aimed at elucidating the distribution of LCs in varying grades of OSMF.

Materials and Methods

A retrospective study using 18 cases of OSMF, graded using haematoxylin and eosin (H&E)-stained section. Immunohistochemistry was performed using polyclonal anti-CD1a antibodies to identify LCs in six cases of normal tissue and 18 samples of OSMF. The distribution of LCs among the various grades and normal mucosa analysed using Student's t-test.

Results

LC population in the OSMF was significantly higher when compared to the normal epithelium (p < 0.001). Within the grades, the advanced stage had more LCs than the other stages.

Conclusion

The increase in LCs might indicate the role of antigenic exposure in turn leading to cell-mediated immunity in OSMF. Thus, the fibrosis in OSMF might have a direct link to LCs.

The Current Understanding on Langerhans' Cells and Its Role in Oral Lesions

OBJECTIVE

Description of Langerhans' cells (LCs) as an important antigen-presenting cells responsible for detecting the antigens, recruiting T-cells, and thereby initiating the immune response. An adequate response of the mucosal immune system is essential to protect the mucosa against pathological conditions. Hence, a detailed review was planned about this unique antigen-presenting cell.

METHODS

A literature search of the electronic databases included the MEDLINE, EBSCOHOST, PUBMED, and hand searches of references retrieved were undertaken using the following MeSH terms "Langerhans cells," "LCs in Oral Lichen Planus," "Langerhans cell histiocytosis," "LCs and HIV," "LCs in Periodontitis."

RESULTS

LCs are present suprabasally in the epithelium of oral mucosa and in the epidermis of the skin. The role played by LCs though not fully elucidated, but several research studies indicate that these cells are involved in the pathogenesis of many oral diseases. In this article, the historical perspective, structure, function, origin, and phenotypic expressions of LCs are discussed in detail. The current understanding on the role of LCs in various oral lesions and its immunological characteristics are discussed.

CONCLUSION

LCs act as immune mediator cells, tumor cells, vectors of infected cells, and phagocytic cells. Further studies could bolster the knowledge about the role of Langerhans cells in the immune response of various oral diseases and thereby provide diagnostic tools and help for prognostic evaluation. This review illuminates the pivotal role of Langerhans cells and its immune surveillance as a "Sentinels" of the oral mucosa.

Expression of Cluster of Differentiation 1a-Positive Langerhans Cells in Oral Lichen Planus

Background/Purpose:

Lichen planus is a T-cell-mediated mucocutaneous disorder characterized histopathologically by a band of chronic inflammatory cells in the subepithelial zone and degeneration of basal layer. The present study was aimed to evaluate the distribution and quantitative assessment of cluster of differentiation 1a (CD1a)-positive Langerhans cells (LCs) in oral lichen planus (OLP), thus to determine the role of LCs pertaining to the changes occurring in OLP.

Materials and Methods:

Five cases of normal oral mucosa and 20 cases of OLP were immunostained with CD1a antibody; the positive cells were counted manually in the photomicrographs and statistically analyzed using t-test, Mann–Whitney test, and Wilcoxon signed-rank test.

Results:

The average percentage of CD1a-positive LCs in normal subjects was 0.9%, and in the OLP cases higher percentage was observed (3.93%). The statistical comparison of these two parameters was significant (P=0.018). The degree of basal cell degeneration and density of subepithelial infiltrate on statistical comparison with the concentration of CD1a-positive LCs showed significant results.

Conclusion:

LCs play a pivotal role in the recruitment of CD4+ and CD8+ cells to the subepithelial region and basal keratinocytes apoptosis. A small number of study subjects, assessment of only CD1a molecule and LCs in the epidermis only were a few of the drawbacks of the study.

Black pepper and its bioactive constituent piperine: promising therapeutic strategies for oral lichen planus

Oral lichen planus (OLP) is a common T cell-mediated chronic inflammatory disease with malignant potential and unclear etiology. The present study suggests that antigen-specific mechanisms in which dentritic cells, T lymphocytes and NF-κB signaling pathway play critical roles, are involved in the pathogenesis of OLP. Additionally, it has been indicated that altered expression of cyclooxygenase 2 (COX-2) and imbalanced oxidant-antioxidant status as well as psychological issue may act as promoters to the development of OLP. Therapies for OLP are primarily aimed to control symptoms and a specific cure is not yet available. Black pepper and its principle bioactive compound piperine have been reported to possess remarkable pharmacological activities. Not only has piperine been evidenced to exhibit repressive effects on the maturation of dentritic cells, the proliferation, activation and function of T lymphocytes as well as the NF-κB signaling pathway, but also to suppress the overproduction of COX-2 and weaken the oxidative stress. Furthermore, piperine might be a possible agent for alleviating psychological disorders and preventing carcinogenesis. Given all these into consideration, piperine may be a novel and effective therapeutic strategy for OLP.

S100 protein-positive Langerhans cells in 80 dentigerous cysts

BACKGROUND/PURPOSE

Langerhans cells (LCs) are antigen-presenting cells. This study assessed the LC counts in 80 dentigerous cysts (DCs).

MATERIALS AND METHODS

The S100-positive LC numbers in the lining epithelia and subepithelial connective tissues were counted at 80 DC sites without inflammation, 33 DC sites with mild/moderate inflammation, and 9 DC sites with severe inflammation from 80 DC specimens.

RESULTS

The mean S100-positive LC counts in the lining epithelia and subepithelial connective tissues increased significantly from no inflammation (0.6 ± 0.6 and 0.7 ± 0.6 cell/high-power field or HPF, respectively) through mild/moderate inflammation (8.1 ± 2.0 and 4.5 ± 2.3 cells/HPF, respectively) to severe inflammation DC sites (21.0 ± 7.0 and 11.1 ± 6.5 cells/HPF, respectively; P-value < 0.001). DC sites with inflammation had thicker lining epithelia than those without inflammation. Moreover, the mean LC counts in the lining epithelia and subepithelial connective tissues of DCs were significantly higher in the thicker lining epithelium (>50 μm) group (8.6 ± 7.1 and 4.8 ± 4.5 cells/HPF, respectively) than in the thinner lining epithelium (≦50 μm) group (0.6 ± 0.6 and 0.6 ± 0.6 cells/HPF, respectively; both P-values < 0.001).

CONCLUSION

A significant association of high-grade inflammation and thick lining epithelium with the increased LC number in DCs is found. Very few LCs in the lining epithelia of DCs without inflammation indicate the reduced immunosurveillance ability against DC lining epithelial cells in DC patients. It needs further studies to confirm the role of reduced immunosurveillance in the enlargement of the DC.

Langerhans cells in 60 odontogenic keratocysts

BACKGROUND/PURPOSE

Langerhans cells (LCs) are antigen-presenting cells. This study mainly evaluated the LC counts in 60 odontogenic keratocysts (OKCs).

MATERIALS AND METHODS

The CD1a-positive LC numbers in the lining epithelia and subepithelial connective tissues were counted at 60 OKC sites without inflammation, 39 OKC sites with mild/moderate inflammation, and 13 OKC sites with severe inflammation from 60 OKC specimens.

RESULTS

The mean CD1a-positive LC counts in the lining epithelia and subepithelial connective tissues increased significantly from no inflammation (0.5 ± 0.4 and 0.2 ± 0.3 cell/high-power field or HPF, respectively) through mild/moderate inflammation (5.3 ± 2.5 and 2.5 ± 2.7 cells/HPF, respectively) to severe inflammation OKC sites (12.7 ± 5.6 and 9.3 ± 7.2 cells/HPF, respectively; all P-values < 0.001). OKC sites with inflammation had thicker lining epithelia than those without inflammation. Moreover, the mean CD1a-positive LC counts in the lining epithelia and subepithelial connective tissues of OKCs were significantly higher in the thicker lining epithelium (>100 μm) group (6.8 ± 5.1 and 3.7 ± 4.9 cells/HPF, respectively) than in the thinner lining epithelium (≦100 μm) group (1.0 ± 1.7 and 0.8 ± 2.5 cell/HPF, respectively; both P-values < 0.001).

CONCLUSION

There is a significant association of inflammation grade with the number of LCs in OKCs. The scarce LCs in the lining epithelia of OKCs without inflammation suggests the loss of immunosurveillance ability against the OKC lining epithelial cells; this can explain why OKCs have aggressive clinical behavior, a great growth potential, and a high recurrence rate.

Significant association of inflammation grade with the number of Langerhans cells in odontogenic keratocysts

BACKGROUND/PURPOSE

Langerhans cells (LCs) are antigen-presenting cells. This study assessed the LC counts in odontogenic keratocysts (OKCs).

METHODS

The LC numbers in the lining epithelia and subepithelial connective tissues were counted at 60 OKC sites without inflammation, 39 OKC sites with mild/moderate inflammation, and 13 OKC sites with severe inflammation from 60 OKC specimens immunostained with anti-S100 antibodies.

RESULTS

The mean LC counts in the lining epithelia and subepithelial connective tissues increased significantly from no inflammation (0.5 ± 0.4 and 0.7 ± 0.6 cell/high-power field or HPF, respectively) through mild/moderate inflammation (5.9 ± 2.7 and 5.0 ± 3.5 cells/HPF, respectively) to severe inflammation OKC sites (14.7 ± 5.3 and 13.3 ± 6.8 cells/HPF, respectively; all P-values < 0.001). OKC sites with inflammation had thicker lining epithelia than those without inflammation. Moreover, the mean LC counts in the lining epithelia and subepithelial connective tissues of OKCs were significantly higher in the thicker lining epithelium (>100 μm) group (7.7 ± 5.6 and 6.5 ± 5.8 cells/HPF, respectively) than in the thinner lining epithelium (≦ 100 μm) group (1.0 ± 2.0 and 1.4 ± 2.6 cells/HPF, respectively; both P-values < 0.001).

CONCLUSION

A significant association of inflammation grade with the number of LCs in OKCs is found. The paucity of finding LCs in the lining epithelia of OKCs without inflammation indicates the loss of immunosurveillance ability against the OKC lining epithelial cells; this can explain why OKCs have aggressive clinical behavior, a great growth potential, and a high recurrence rate.

Comparative phenotypic and functional analysis of migratory dendritic cell subsets from human oral mucosa and skin

Antigen exposure to oral mucosa is generally thought to lead to immune tolerance induction. However, very little is known about the subset composition and function of dendritic cells (DC) migrating from human oral mucosa. Here we show that migratory DC from healthy human gingival explants consist of the same phenotypic subsets in the same frequency distribution as DC migrating from human skin. The gingival CD1a+ Langerhans cell and interstitial DC subsets lacked CXCR4 expression in contrast to their cutaneous counterparts, pointing to different migration mechanisms, consistent with previous observations in constructed skin and gingival equivalents. Remarkably, without any exogenous conditioning, gingival explants released higher levels of inflammatory cytokines than human skin explants, resulting in higher DC migration rates and a superior ability of migrated DC to prime allogeneic T cells and to induce type-1 effector T cell differentiation. From these observations we conclude that rather than an intrinsic ability to induce T cell tolerance, DC migrating from oral mucosa may have a propensity to induce effector T cell immunity and maintain a high state of alert against possible pathogenic intruders in the steady state. These findings may have implications for oral immunization strategies.

Langerhans cell counts in oral epithelial dysplasia and their correlation to clinicopathological parameters

BACKGROUND/PURPOSE

Langerhans cells (LCs) are antigen presenting cells. This study assessed the LC counts in oral epithelial dysplasia (OED) and their correlation to clinicopathological parameters.

METHODS

This study examined the LC counts in the epithelia and subepithelial connective tissues of 58 patients with OED (21 mild, 18 moderate, and 19 severe OED lesions) and 10 specimens of normal oral mucosa (NOM) by anti-S-100 protein immunostaining.

RESULTS

We found that the mean LC counts in the epithelia or subepithelial connective tissues increased significantly from NOM samples through mild and moderate OED to severe OED samples. In addition, a significant correlation was found between higher mean LC counts in the dysplastic epithelia of OED samples and OED lesions with thicker epithelial layers (p<0.001) or wider inflammatory zones (p<0.001), and between higher mean LC counts in the subepithelial connective tissues of OED samples and OED lesions with wider inflammatory zones (p<0.001). Moreover, the nine OED lesions with malignant transformation had a significantly lower mean LC count than the 49 OED lesions without malignant transformation.

CONCLUSION

The significant and gradual elevation in LC count from NOM through mild and moderate OED to severe OED lesions suggests an upregulation of immunosurveillance ability in OED patients during the early oral carcinogenesis process. A low LC count in OED lesions may suggest the partial loss of immunosurveillance ability against dysplastic cells; this in turn favors the malignant transformation of an OED lesion into oral cancer.

Phenotype and Tissue Residency of Lymphocytes in the Murine Oral Mucosa

The oral mucosa is a critical barrier tissue that harbors a series of distinct immune cell subsets. Immune surveillance in the oral mucosa is important for both local and systemic immunity because the oral cavity is a heavily utilized route of pathogen entry and also serves as site of pathogen propagation. Nonetheless, composition and phenotype of the lymphocyte pool in the oral mucosa have remained poorly characterized. Utilizing a newly established protocol for mucosal immune cell isolation, here, we report that the oral mucosa features a unique cellular composition of immune cells, which differed not only from secondary lymphoid organs but also from mucosal tissues in the gut and lung. We observed profound accumulation of CD11b⁺Ly6C^lo monocytes in the oral mucosa that were maintained independently of T- and B-lymphocytes. Unlike the gut mucosa, the oral mucosa neither contained CD8αα T cells nor was it enriched for CD103⁺CD69⁺ tissue-resident memory CD8 T cells. In fact, a major fraction of T cells circulated and trafficked through the mucosa as revealed by treatment with the S1P1 receptor antagonist, FTY720, a potent inhibitor of lymphocyte migration. Collectively, these results provide a comprehensive picture of immune cells in the oral mucosa as an active site of lymphocyte recruitment and surveillance.

On the pathogenesis of mTOR inhibitor-associated stomatitis (mIAS)-studies using an organotypic model of the oral mucosa

OBJECTIVE

mTOR inhibitor treatment of solid cancers is associated with mTOR inhibitor-associated stomatitis (mIAS) a common, significant, dose-limiting toxicity, with aphthous-like lesions. Our objective was to assess the utility of a new organotypic model in defining mIAS' pathogenesis.

MATERIALS AND METHODS

The effect of everolimus on organotypic human oral mucosa was studied. Sterile specimens were assessed 24 and 48 h after exposure to varying concentrations of everolimus. Morphologic changes and measures of apoptosis, proliferation, and levels of six Th1 and Th2 cytokines were studied.

RESULTS

Following a 24-h incubation, concentrations of 500 ng ml^-1 of everolimus resulted in histological changes consistent with epithelial injury, disorganization and pre- or early apoptosis, increased TUNEL-positive staining (P < 0.05) and reduced PCNA-positive staining cells (P < 0.001) and increased levels of IL-6 (P < 0.0001), IL-8 (P < 0.01), and IFN-γ (P < 0.09).

CONCLUSIONS

Everolimus elicited epithelial damage manifest by morphologic changes, increased apoptosis, and decreased proliferation with concurrent release of keratinocyte-derived pro-inflammatory cytokines in the absence of bacteria. The extent of the effect was concentration and time dependent. These results suggest that mIAS is likely initiated by direct epithelial injury, independent of the microbiome. Keratinocyte cytokine release could likely play a role in accelerating an inflammatory infiltrate.

Mucosal vaccine delivery: Current state and a pediatric perspective

Most childhood infections occur via the mucosal surfaces, however, parenterally delivered vaccines are unable to induce protective immunity at these surfaces. In contrast, delivery of vaccines via the mucosal routes can allow antigens to interact with the mucosa-associated lymphoid tissue (MALT) to induce both mucosal and systemic immunity. The induced mucosal immunity can neutralize the pathogen on the mucosal surface before it can cause infection. In addition to reinforcing the defense at mucosal surfaces, mucosal vaccination is also expected to be needle-free, which can eliminate pain and the fear of vaccination. Thus, mucosal vaccination is highly appealing, especially for the pediatric population. However, vaccine delivery across mucosal surfaces is challenging because of the different barriers that naturally exist at the various mucosal surfaces to keep the pathogens out. There have been significant developments in delivery systems for mucosal vaccination. In this review we provide an introduction to the MALT, highlight barriers to vaccine delivery at different mucosal surfaces, discuss different approaches that have been investigated for vaccine delivery across mucosal surfaces, and conclude with an assessment of perspectives for mucosal vaccination in the context of the pediatric population.

The predictive value of dendritic cells in early squamous cell carcinoma of the tongue

OBJECTIVES

The aim of this study was to evaluate the relationship between dendritic cell density in early squamous cell carcinoma (SCC) of the tongue and patients' clinical outcome.

METHODS

Representative samples of low-risk SCC of the tongue (T1-2,N0,M0) from a homogeneous group of 18 patients following local complete excision and elective selective neck dissection, were immunostained with antibodies against S100 and CD1a. Dendritic cell density was analyzed by outcome.

RESULTS

Mean dendritic cell densities were 17 cells/HPF for tumoral S100 and CD1a counts, and 10 cells/HPF for peritumoral S100 and CD1a counts. Better disease-free survival was associated with low peritumoral S100- and CD1a- positive cell counts (p=0.006 and p=0.004, respectively), and with low tumoral S100- and CD1a- positive cell counts (p=0.037 and p=0.04, respectively). Lymphocytic response was decreased in tumors with high dendritic cell density (p=NS). There was no association of dendritic cell density with patient age, tumor size and depth of invasion.

CONCLUSIONS

These results may suggest an association between dendritic cell accumulation and functional immunologic impairment.

Activation of Langerhans-Type Dendritic Cells Alters Human Cytomegalovirus Infection and Reactivation in a Stimulus-Dependent Manner

Oral mucosal Langerhans cells (LC) are likely to play important roles in host defense against infection by human cytomegalovirus (CMV). We previously showed that in vitro-differentiated immature LC (iLC) populations contain smaller amounts of infected cells but produce higher yields than mature LC (mLC) cultures, obtained by iLC stimulation with fetal bovine serum (FBS), CD40 ligand (CD40L) and lipopolysaccharide (LPS). Here, we sought to determine if exposure to select stimuli can improve LC permissiveness to infection, if specific components of the mLC cocktail are responsible for lowering viral yields, if this is due to defects in progeny production or release, and if these restrictions are also effective against reactivated virus. None of the stimuli tested extended the proportion of infected cells to 100%, suggesting that the block to infection onset cannot be fully removed. While CD40L and FBS exerted positive effects on viral progeny production per cell, stimulation with LPS alone or in combination with CD40L was detrimental. Reductions in viral titers were not due to defects in progeny release, and the permissive or restrictive intracellular environment established upon exposure to each stimulus appeared to act in a somewhat similar way toward lytic and latent infections.

Langerhans cell number is a strong and independent prognostic factor for head and neck squamous cell carcinomas

OBJECTIVES

Head and neck squamous cell carcinomas (HNSCCs) exhibit great biological heterogeneity and relatively poor prognosis. Tobacco and alcohol consumption is involved in the cause of the majority of these cancers, but over the last several years, Human Papilloma Virus (HPV) infection has increased specifically in oropharyngeal cancers and become an additional risk factor. Here, we evaluated the number of Langerhans cells (LCs) in HNSCC and reporting its prognostic power in comparison to other risk factors.

MATERIALS AND METHODS

Our clinical series was composed of 25 tumor-free peritumoral epithelium, 64 low-grade dysplasia, 54 high-grade dysplasia and 125 carcinoma samples. HPV was detected by E6/E7 qPCR and p16 immunohistochemistry. CD1a-positive LCs were counted in intra-tumoral and stromal compartments as well as lymph nodes. MIP-3α was assessed in carcinomas using immunohistochemistry.

RESULTS

Univariate Cox regression analyses demonstrated that high LC number is associated with longer recurrence-free survival in both intra-tumoral and stromal compartments and longer overall survival in stromal compartment. Tobacco and alcohol habits, but not HPV status, are also correlated with poor prognoses in terms of recurrence. Multivariate analyses reported stromal LC number as a strong prognostic factor independent of tobacco, alcohol and HPV status. Moreover, LC number is higher in tumors and invaded lymph nodes than dysplastic lesions but it decreases in HPV-positive cancer patients. Further, LC number correlates with MIP-3α expression.

CONCLUSION

These findings suggest that LC number is a significant and independent prognostic factor for HNSCC. LC infiltration is increased in cancer lesions but decrease with HPV infection.

Expression of CD1a by Langerhan's Cells in Oral Lichen Planus - A Retrospective Analysis

INTRODUCTION

Langerhan's Cells (LCs) are dendritic cells of the oral epithelium which play a role in a series of oral lesions from gingivitis to oral cancer. Oral Lichen Planus (OLP) is an oral mucosal T-lymphocyte mediated immunologic reaction to an unidentified putative antigen or allergen.

AIM

The aim of this study was to quantify the presence of immature LCs in OLP comparing them with normal epithelium.

MATERIALS AND METHODS

A retrospective study using 30 of OLP cases were conducted. Immunohistochemistry was performed using polyclonal anti-CD1a antibodies to identify LCs in 10 cases of normal tissue and 30 samples of OLP. The distribution of LCs among lesional tissue and normal mucosa was analysed using Mann-Whitney U test.

RESULTS

LC population in OLP was significantly higher when compared to the normal epithelium (p<0.001).

CONCLUSION

The increase in LCs indicates the active role played during the antigen detection in OLP and subsequent presentation to T-lymphocytes.

Role of abnormal Langerhans cells in oral epithelial dysplasia and oral squamous cell carcinoma: A pilot study

BACKGROUND

The oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC), although initiated by tobacco carcinogens, their progression is due to inability of Langerhans cells (LCs) to detect these abnormal cells and promote lymphocytes to destroy these cells. We assessed and quantified the tumor associated LCs and inflammation in OED and OSCC to understand their role.

MATERIALS AND METHODS

Fifty-five microscopic sections were assessed (27 OED and 28 OSCC). The LCs were detected using S-100 immunohistochemical marker. The number of tumor associated LCs were counted. The presence of abnormal appearing large cells and its relation to histopathologic grade and inflammation was assessed.

RESULTS

Significant increase in the LC count was observed in OSCC when compared to dysplasia. Large, abnormal appearing cells were observed in dysplasia and carcinomas however, these were more pronounced in moderate dysplasia and poorly-differentiated carcinomas. The presence of these abnormal appearing cells was associated with decrease in lymphocytic infiltrate.

CONCLUSION

The present study indicates more LC are recruited into the carcinoma. These accumulated nonfunctional LC in the tumor tissue are indicative of aggressive tumor with potential malignant transformation.

Langerhans cell-like dendritic cells stimulated with an adjuvant direct the development of Th1 and Th2 cells in vivo

It is well known that Langerhans cells (LCs) work as the primary orchestrators in the polarization of immune responses towards a T helper type 1 (Th1) or Th2 milieu. In this study, we attempted to generate LCs from murine bone marrow cells and elicit a Th1- or Th2-prone immune response through the LCs after stimulation with Th1 or Th2 adjuvant. LCs were generated from murine bone marrow cells using granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-4 and transforming growth factor (TGF)-β, and were obtained as I-A(d) positive cells. Mice were primed with Th1/Th2 adjuvant- and ovalbumin (OVA)-pulsed LCs and then given a booster injection of OVA 2 days later via the hind footpad. Five days after the OVA injection, the cytokine response in the draining popliteal lymph nodes was investigated by reverse transcription-polymerase chain reaction (RT-PCR) flow cytometry and enzyme-linked immunosorbent assay (ELISA). The generated LCs expressed typical LC surface markers, E-cadherin and Langerin, and were classified accordingly as LC-like dendritic cells (LDCs). Administration of Th1 adjuvant, cytosine-phosphate-guanosine (CpG)-DNA- and OVA-pulsed LDCs into the hind footpads of mice induced a Th1-prone immune response, as represented by up-regulation of IFN-γ production and down-regulation of IL-4 production in the lymph node cells. Conversely, Th2 adjuvant, histamine-pulsed LDCs induced a Th2-prone immune response, as represented by up-regulation of IL-4 production and down-regulation of IFN-γ production. These results suggest that LDCs may be used as a substitute for LCs and have the ability to induce the development of Th1 and Th2 cells in vivo. Our experimental system would therefore be useful for screening of inhibitors of Th1/Th2 differentiation in order to control allergic disease.

Dynamics of Human Cytomegalovirus Infection in CD34+ Hematopoietic Cells and Derived Langerhans-Type Dendritic Cells

Acquisition of human cytomegalovirus (CMV) usually occurs by contact between contaminated bodily fluids, such as urine and saliva, and host mucosal cells. Langerhans-type dendritic cells (LC) are the only type of immune cells found in the outermost layers of the oral mucosae, where they not only provide a first line of defense against CMV but can easily be targeted by orally administered vaccines, while their bone marrow resident progenitors are important sites of virus latency. In this work, we tracked the progress of infection in CD34(+) progenitor cells, immature LC (iLC), and mature LC (mLC) exposed to the clinical-like strain TB40-BAC4 or to the vaccine strain AD169varATCC, prior to their long-term maintenance under either immature or mature conditions. We show that the genomes of both strains are efficiently maintained in CD34(+) cells during their differentiation into iLC, although this requires the presence of larger amounts of input AD169varATCC DNA. Lipopolysaccharide- and CD40 ligand-induced maturation of iLC derived from latently infected progenitors was not associated with robust viral genome replication and progeny production, while maturation of directly infected iLC increased and prolonged expression of the viral immediate early proteins. While effective replication of viral genomes from both strains occurred only in mLC, both iLC and mLC produced viral progeny, suggesting that both types of LC may contribute to CMV horizontal transmission in vivo.

IMPORTANCE

Human CMV is usually acquired via the oral and nasal mucosae. Langerhans-type dendritic cells (LC) are the only type of immune cells found in the outermost layers of these tissues. Understanding how CMV interacts with LC and their hematopoietic progenitors is thus essential to develop innovative means of defense against this virus. Here we show that the genomes of a virulent and an attenuated strain of CMV are maintained in hematopoietic progenitor cells during their differentiation into immature LC and that maturation of these cells by exposure to lipopolysaccharide and CD40 ligand is not sufficient to trigger virus reactivation. While the extents of viral protein expression and genome replication were broadest in directly infected mature LC populations, similar amounts of viral progeny were detected in the supernatants of immature and mature LC, suggesting that these immune cells of the oral mucosa are likely to be important for CMV transmission within the human population.

The mucosal immune system in the oral cavity-an orchestra of T cell diversity

The mucosal immune system defends against a vast array of pathogens, yet it exhibits limited responses to commensal microorganisms under healthy conditions. The oral-pharyngeal cavity, the gateway for both the gastrointestinal and respiratory tracts, is composed of complex anatomical structures and is constantly challenged by antigens from air and food. The mucosal immune system of the oral-pharyngeal cavity must prevent pathogen entry while maintaining immune homeostasis, which is achieved via a range of mechanisms that are similar or different to those utilized by the gastrointestinal immune system. In this review, we summarize the features of the mucosal immune system, focusing on T cell subsets and their functions. We also discuss our current understanding of the oral-pharyngeal mucosal immune system.

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.

Liquid crystalline epoxy nanocomposite material for dental application

BACKGROUND/PURPOSE

Novel liquid crystalline epoxy nanocomposites, which exhibit reduced polymerization shrinkage and effectively bond to tooth structures, can be applied in esthetic dentistry, including core and post systems, direct and indirect restorations, and dental brackets. The purposes of this study were to investigate the properties of liquid crystalline epoxy nanocomposites including biocompatibility, microhardness, and frictional forces of bracket-like blocks with different filler contents for further clinical applications.

METHODS

In this study, we evaluated liquid crystalline epoxy nanocomposite materials that exhibited various filler contents, by assessing their cell activity performance using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and their microhardness with or without thermocycling. We also evaluated the frictional force between bracket-like duplicates and commercially available esthetic bracket systems using Instron 5566.

RESULTS

The liquid crystalline epoxy nanocomposite materials showed good biocompatibility. The materials having high filler content demonstrated greater microhardness compared with commercially available bracket materials, before and after the thermocycling treatment. Thus, manufacturing processes are important to reduce frictional force experienced by orthodontic brackets.

CONCLUSION

The microhardness of the bracket-like blocks made by our new material is superior to the commercially available brackets, even after thermocycling. Our results indicate that the evaluated liquid crystalline epoxy nanocomposite materials are of an appropriate quality for application in dental core and post systems and in various restorations. By applying technology to refine manufacturing processes, these new materials could also be used to fabricate esthetic brackets for orthodontic treatment.

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.

Langerhans cells in the human tympanic membrane in health and disease: a morphometric analysis

HYPOTHESIS

The normal tympanic membrane contains Langerhans dendritic cells, and they play a role in the pathogenesis of chronic suppurative otitis media.

BACKGROUND

The presence of Langerhans dendritic cells in the normal tympanic membrane is disputed. However, they have been identified in tympanic membranes of patients with otitis media. A quantitative analysis of the distribution and morphology of these cells in the types of chronic suppurative otitis media has not been undertaken.

METHODS

Samples of normal cadaveric tympanic membranes and those from patients with chronic suppurative otitis media of the tubotympanic and atticoantral varieties were stained with the immunohistochemical marker CD1a. The number of cells per unit length of basement membrane, diameters of cells, and number and length of dendritic processes were compared between the groups.

RESULTS

CD1a-positive Langerhans dendritic cells were present in the normal tympanic membrane. The number of cells per unit length of basement membrane, diameters of cells, and the length of dendritic processes increased significantly in tubotympanic disease and in atticoantral disease, the difference being more pronounced in the latter form of otitis media.

CONCLUSION

Langerhans cells are present in the normal tympanic membrane, and they probably play differing roles in the pathogenesis of tubotympanic and atticoantral forms of chronic suppurative otitis media.

Immune alterations and immunotherapy prospects in head and neck cancer

INTRODUCTION

Several literature sources have suggested that subjects with head and neck squamous cell carcinoma (HNSCC) display significant abnormalities of immunocompetent cells and cytokine secretion. Serious side effects and only a limited success with traditional therapies in HNSCC dictate the need for newer therapies.

AREAS COVERED

This article comprehensively reviews the immune system alterations in HNSCC and the rationale behind various experimental immunotherapies, aiming at keeping this disease under control. Relevant publications were identified through the PubMed database search. The ongoing clinical trials regarding experimental immunotherapy agents in HNSCC were accessed at www.clinicaltrials.gov . The obtained information was thoroughly analyzed and systematized.

EXPERT OPINION

Important and severe immune defects including T-cell dysfunction, cytokine alterations and antigen presentation defects are present in patients with HNSCC. In addition, tumor microenvironment was shown to play a critical role in the HNSCC progression. These discoveries have triggered a growing interest in immunotherapy as a potential treatment strategy for HNSCC. Effective immunotherapy could avoid the toxic side effects plaguing the current management of HNSCC. It is also hoped that immunotherapy will have long-lasting effects due to induction of immunologic memory. Promising directions include nonspecific immune stimulation, targeting specific HNSCC tumor antigens and therapeutic vaccines among others. These new agents may expand the existing therapy options for HNSCC in future.

Oral lichen planus: focus on etiopathogenesis

Lichen planus is a chronic mucocutaneous inflammatory disease, which frequently affects the oral mucosa of white females over 40 years old. Its aetiology remains uncertain and the pathogenesis is still the object of much speculation. The present paper presents the most well known antigens, and describes the action of different cells and proteins associated with the development of that disease, as well as the possible agents involved with its malignant transformation. Different external agents, especially virus, and internal agents, like stress, and the heat shock protein antigen expression, associated or not, can alter the basal keratinocytes of the oral mucosa making them susceptible to apoptosis by CD8(+) cytotoxic T cell as well as activate matrix metalloproteinase and mast cell degranulation, which produce a great range of inflammatory mediators and cytokines determining the clinical onset of the disease. Regarding carcinogenesis, since it is a complex process and presents multifactorial origin, it is believed that there may be a synergism between intrinsic, such as inflammation mediators, and extrinsic agents (tobacco, alcohol, viral infections) for the OLP malignant transformation to occur. However, further studies are needed to better understand the origin, pathogenesis and process of malignant transformation of OLP.

Immunohistological analysis of CD1a langerhans cells and CD57 natural killer cells in healthy and diseased human gingival tissue: A comparative study

Background:

Cell interaction between dendritic cells (DC) and natural killer (NK) cells in the periodontal milieu is not yet fully known, although these cells are individually known to contribute to the pathogenesis of periodontal disease.

Materials and Methods:

Fifty subjects (25 males and 25 females) were included in the study. The subjects were divided into three groups: Group A comprised 16 subjects with clinically healthy gingiva; group B 17 subjects with gingivitis; and group C 17 subjects with gingivitis; and group C 17 subjects with moderate periodontitis (PPD ≥ 5 mm and CAL ≥ 3 mm in at least six sites). Gingival samples were collected and immunohistochemical study was done using CD57 and CD1a antibody. Statistical analysis was done using analysis of variance (ANOVA), followed by Tukey-Kramer multiple comparison for CD1a and Tukey's highly significant difference (HSD) test for CD57.

Results and Conclusion:

The study showed an inverse relationship between the CD1a⁺ (langerhans) cells and CD57⁺ (natural killer) cells. There was a significant increase in CD57⁺ cells and reduction in CD1a levels as periodontal disease progressed. The significant reduction in CD1a levels in periodontal disease when compared to health could possibly be a result of NK cells down regulating it. Reduction in CD1a levels may result in a low inflammatory response subsequently resulting in tissue destruction.

Immune suppression in head and neck cancers: a review

Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common cancer in the world. Despite significant advances in the treatment modalities involving surgery, radiotherapy, and concomitant chemoradiotherapy, the 5-year survival rate remained below 50% for the past 30 years. The worse prognosis of these cancers must certainly be link to the fact that HNSCCs strongly influence the host immune system. We present a critical review of our understanding of the HNSCC escape to the antitumor immune response such as a downregulation of HLA class I and/or components of APM. Antitumor responses of HNSCC patients are compromised in the presence of functional defects or apoptosis of T-cells, both circulating and tumor-infiltrating. Langerhans cells are increased in the first steps of the carcinogenesis but decreased in invasive carcinomas. The accumulation of macrophages in the peritumoral areas seems to play a protumoral role by secreting VEGF and stimulating the neoangiogenesis.

Effect of a topical antimicrobial paste on healing after extraction of molars in HIV positive patients: Randomised controlled clinical trial

AIM

To assess the efficacy of a medicated dressing in the socket on the healing after dental extractions in HIV positive patients.

PATIENTS AND METHODS

Forty HIV positive patients with CD4 counts below 200 cells/mm(3) who were to have molar teeth extracted were randomly allocated to have the socket dressed with a medicated paste (Rifocort) with camphorated parachlorophenol and iodoform) and sutured (treated group), or merely sutured (control group).

RESULTS

The sockets in the treated group healed more quickly than in the control group.

Do Langerhans cells behave similarly in elderly and younger patients with chronic periodontitis?

OBJECTIVE

The purpose of this study was to compare the number, the distribution and the expression of markers of maturation of Langerhans cells (LC) in elderly and younger patients with chronic periodontitis in order to evidence the effect of aging on LC in inflammatory gingival tissue.

METHODS

Gingival tissue specimens presenting chronic periodontitis from 8 elderly patients aged >75 (group E) and from 8 younger patients aged 50-60 (considered as controls, group C) were used for immunohistochemistry with monoclonal antibodies against CD45RB (leucocytes), CD1a (LC), markers of LC maturation (DC-LAMP, CD83) and number of immunolabelled cell subsets was evaluated using image analysis.

RESULTS

The difference in the number of CD45RB+ leucocytes in the upper connective tissue between groups was not significant. In group E, the number of CD1a+ LC was significantly decreased (P<0.002) in the epithelium and significantly increased (P<0.0004) in the upper connective tissue. Furthermore, in group E, intraepithelial CD1a+ LC are more often observed in the upper epithelium and their dendritic processes were shorter and less numerous. Concerning the expression of markers of maturation, the numbers of intraepithelial DC-LAMP+ cells and CD83+ cells were significantly increased (P<0.0007 and P<0.02, respectively) in group E.

CONCLUSION

During chronic periodontitis in elderly patients, the decrease in the number of intraepithelial LC and the alteration of dendritic processes could be balanced by a cellular distribution often observed in the upper epithelium associated with changes in cell maturation in response to bacterial elements.

Langerhans cells express matrix metalloproteinases 9 and 2 and tissue inhibitors of metalloproteinases 1 and 2 in healthy human gingival tissue and in periodontitis

BACKGROUND

As antigen-presenting cells, Langerhans cells may play an important role in the initiation and maintenance of periodontal disease. This study is the first report that extends our knowledge of the expression of matrix metalloproteinases and their endogenous tissue inhibitors by Langerhans cells in healthy and diseased gingival tissues.

METHODS

Single and double immunolabeling procedures were carried out using monoclonal antibodies against CD1a, matrix metalloproteinases 2 and 9, and tissue inhibitors of matrix metalloproteinases 1 and 2, and analyzed by conventional and confocal microscopes.

RESULTS

Langerhans cells expressed matrix metalloproteinases 2 and 9, and tissue inhibitors of matrix metalloproteinases 1 and 2 in healthy and diseased gingival tissues. The tissue inhibitors of matrix metalloproteinase-positive Langerhans cells were mainly observed in the upper epithelial layers. Matrix metalloproteinase 9-positive Langerhans cells were observed especially during periodontitis and in the basal epithelial layer or crossing the basement membrane.

CONCLUSION

During periodontal disease, changes in the expression of matrix metalloproteinases and their tissue inhibitors by gingival Langerhans cells could be implicated in the migration of the cells towards the connective tissue.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Gingival organotypic culture and langerhans cells: a tool for immunotoxicologic experiments

Langerhans cells (LCs) are dendritic cells localized in epidermis and mucosal tissues, where they are responsible for triggering the immune response. To study LCs in the oral epithelium, organotypic cultures were prepared using gingival explants. Immunochemical techniques using anti-CD1a, anti-HLA-DR, and anti-Langerin antibodies were used to detect and quantify LCs at various times. Observations were made by light and confocal microscopy. Quantification studies showed that there is a statistically significant drop in LC numbers in the epithelial tissue after 96 h of incubation. Gingival organotypic cultures thus are a good model for studying the migration of LCs and their involvement in contact hypersensitivity and periodontal diseases. The model offers potential utility as a tool for the study of periodontal tissue in the presence of different stimuli and for conducting immunotoxicologic experiments.

Powder and particle-mediated approaches for delivery of DNA and protein vaccines into the epidermis

The epidermis of the skin is both a sensitive immune organ and a practical target site for vaccine administration. However, administration of vaccines into the epidermis is difficult to achieve using conventional vaccine delivery methods employing a needle and syringe. A needle-free vaccine delivery system has been developed that efficiently delivers powdered or particulate DNA and protein vaccines into the epidermal tissue. The delivery system can be used to directly transfect antigen presenting cells (APCs) by formulating DNA or protein vaccines onto gold particles (particle-mediated immunization). Antigen can be directly presented to the immune system by the transfected APCs. Antigen can also be expressed and secreted by transfected keratinocytes and picked up by resident APCs through the exogenous antigen presentation pathway. Alternatively, protein antigens can be formulated into a powder and delivered into the extracellular environment where they are picked up by APCs (epidermal powder immunization). Using any of these formulations, epidermal immunization offers the advantage of efficiently delivering vaccines into the APC-rich epidermis. Recent studies demonstrate that epidermal vaccine delivery induces humoral, cellular, and protective immune responses against infectious diseases in both laboratory animals and man.

Immunohistochemical identification of antigen presenting cells in rat salivary glands

Mucosal dendritic cells affect immune responses through secretion of cytokines and exposure of naïve B- and T-lymphocytes to foreign matter as antigen presenting cells (APCs). APC in oral tissues may play a role in the development of local and secretory immune responses [Crit. Rev. Oral Biol. Med. 7 (1996) 36]. Previous studies have shown that APC are present in the interstitial tissues of rat salivary glands [Arch. Oral Biol. 40 (1995) 1015]. This study sought to further define the distribution of APC in salivary glands. The major glands and ducts of male Sprague-Dawley and Wistar rats were fixed with 4% paraformaldehyde and prepared for immunofluorescence and pre- and post-embedding immunoelectron microscopy. Monoclonal antibodies to the dendritic cell marker Ia antigen (OX-6 antibody), monocyte lineage cytoplasmic antigen (ED-1), and resident tissue macrophage antigen (ED-2) were visualized with FITC-conjugated secondary antibodies for light microscopy and HRP- and gold-labelled secondary antibodies for electron microscopy. Light microscopy revealed numerous OX-6-positive cells with branching processes in the epithelium of striated and excretory ducts of both rat strains, as well as in the connective tissue stroma. ED-1-positive cells had a similar distribution but exhibited a more compact shape with fewer processes. ED-2-positive cells were found only in the connective tissue. Acinar and duct epithelial cells were unreactive. Electron microscopy confirmed that both OX-6-positive and ED-1-positive, non-epithelial cells were present within the duct epithelium. The presence of APC in the duct epithelium suggests that these ducts may be exposed to antigens, possibly by retrograde access from the oral cavity, and that APC located in the salivary gland epithelium may participate in local immune responses.

Langerin+ versus CD1a+ Langerhans cells in human gingival tissue: a comparative and quantitative immunohistochemical study

Langerhans cells (LC) are dendritic cells of the immune system able to capture intraepithelial pathogens and migrate to regional lymph nodes to present them to naive T cells. Up to now immunohistological studies on human gingival LC have been carried out using antibodies against HLA-DR or CD1a molecules. A new marker of LC called Langerin (CD207) and described, among other subcellular localisations, in the Birbeck granules is now available in immunohistochemistry. The purpose of this in situ study was to quantify and to compare Langerin+ versus CD1a+ LC number in order to show differences in the expression of these molecules, if any, and to determine which marker is the most specific. The present study was conducted using nine frozen healthy gingival samples. Double immunofluorescence procedures were performed with an anti-Langerin antibody revealed by FITC and with an anti-CD1a-PE antibody. Mounted slides were analysed by fluorescence microscopy and quantifications were performed on projected slides associated with a grid of 0.015 mm(2). Our results have shown that 1/ the number of CD1a+ LC was significantly increased (P=0.01) when compared with Langerin+ LC 2/ 92% of Langerin+ LC co-expressed CD1a 3/ only 82% of CD1a+ cells co-expressed Langerin 4/ a positive correlation was noted between CD1a+ and Langerin+ LC numbers. The present study has revealed the heterogeneity in the phenotype of gingival LC population and shown that Langerin seems the most specific marker for the study of LC.

Langerhans cell-like dendritic cells in the cornea, tongue and oesophagus of the chicken (Gallus gallus)

Langerhans cells are dendritic leucocytes which reside mainly within stratified squamous epithelia of skin and mucosa. Their visualization requires the use of ATPase histochemistry, electron microscopy for identifying the unique trilaminar cytoplasmic organelles (the Langerhans cell granules or Birbeck granules), and the expression of major histocompatibility complex class II molecules. Following uptake of antigen, Langerhans cells migrate via the afferent lymphatics to the lymph nodes and undergo differentiation from an antigen-processing cell to an antigen-presenting cell. Using the same approach as that employed in previous studies for the identification of chicken epidermal Langerhans cells, we show here the presence of ATPase-positive and major histocompatibility complex class II-positive Langerhans cell-like dendritic cells at the mucosal surface of the eye, tongue and oesophagus of the chicken. Ultrastructurally, these cells qualified as Langerhans cells except that they lack Langerhans cell granules. Thus, as in mammalian skin and mucosa, chicken mucosa contains mucosal dendritic cells with morphological and phenotypical features for the engagement of incoming antigens within epithelium and lamina propria.

Tissue compatibility of two biodegradable tubular scaffolds implanted adjacent to skin or buccal mucosa in mice

Radiation therapy for cancer in the head and neck region leads to a marked loss of salivary gland parenchyma, resulting in a severe reduction of salivary secretions. Currently, there is no satisfactory treatment for these patients. To address this problem, we are using both tissue engineering and gene transfer principles to develop an orally implantable, artificial fluid-secreting device. In the present study, we examined the tissue compatibility of two biodegradable substrata potentially useful in fabricating such a device. We implanted in Balb/c mice tubular scaffolds of poly-L-lactic acid (PLLA), poly-glycolic acid coated with PLLA (PGA/PLLA), or nothing (sham-operated controls) either beneath the skin on the back, a site widely used in earlier toxicity and biocompatibility studies, or adjacent to the buccal mucosa, a site quite different functionally and immunologically. At 1, 3, 7, 14, and 28 days postimplantation, implant sites were examined histologically, and systemic responses were assessed by conventional clinical chemistry and hematology analyses. Inflammatory responses in the connective tissue were similar regardless of site or type of polymer implant used. However, inflammatory reactions were shorter and without epithelioid and giant cells in sham-operated controls. Also, biodegradation proceeded more slowly with the PLLA tubules than with the PGA/PLLA tubules. No significant changes in clinical chemistry and hematology were seen due to the implantation of tubular scaffolds. These results indicate that the tissue responses to PLLA and PGA/PLLA scaffolds are generally similar in areas subjacent to skin in the back and oral cavity. However, these studies also identified several potentially significant concerns that must be addressed prior to initiating any clinical applications of this device.

Bilayer films for mucosal (genetic) immunization via the buccal route in rabbits

PURPOSE

The oral buccal mucosa may be an ideal site for mucosal immunization, allowing for the needle-free administration of cost-effective vaccines. A novel mucoadhesive bilayer film was developed to test the feasibility of this route of immunization in rabbits.

METHODS

Bilayer films were developed using different ratios of Noveon and Eudragit S-100 as the mucoadhesive layer and a pharmaceutical wax as the impermeable backing layer. Optimal 3/8-inch films were post-loaded with 100 microg of plasmid DNA (CMV-beta-gal) or beta-galactosidase protein. The in vitro release rates and stability of the postloaded antigens were determined. The films were applied to the buccal pouch of rabbits on days 0. 7, and 14, and the humoral and splenocyte proliferative immune responses to beta-gal were determined through day 28 and compared to those responses after conventional subcutaneous injection of adjuvanted protein.

RESULTS

The weight ratio of Noveon and Eudragit S-100 had a significant effect on adhesion time of bilayer films. Postloaded plasmid DNA and beta-gal remained stable after being released from bilayer films (release of -60-80% in 2 h for both). Buccal immunization using novel bilayer films (109 +/- 6-microm thickness) containing plasmid DNA led to comparable antigen-specific IgG titer to that of subcutaneous protein injection. All rabbits immunized with plasmid DNA via the buccal route but none by the subcutaneous route with protein antigen demonstrated splenocyte proliferative immune responses.

CONCLUSION

The feasibility of buccal (genetic) immunization with these novel bilayer films was demonstrated.

Gene gun-mediated oral mucosal transfer of interleukin 12 cDNA coupled with an irradiated melanoma vaccine in a hamster model: successful treatment of oral melanoma and distant skin lesion

Malignant melanoma involving the oral cavity has a highly metastatic potential. Curative surgery is required to resect extensive oral tissues and often results in dysfunction as well as a severe cosmetic deformity in patients with the disease. An alternative technology for the local and sustained delivery of cytokines for cancer immunotherapy has been shown to induce tumor regression, suppression of metastasis, and development of systemic antitumor immunity. However, local immunization of the oral cavity has not previously been studied. In this study, we examined the efficacy of particle-mediated oral gene transfer on luciferase and green fluorescent protein production. The results showed that these proteins were more significantly expressed in oral mucosa than the skin, stomach, liver, and muscle. Using an established oral melanoma model in hamsters, particle-mediated oral gene gun therapy with interleukin (IL) 12 cDNA was then conducted. The results indicated that direct bombardment of mouse IL-12 cDNA suppressed tumor formation and improved the survival rate. The skin tumor model created by inoculation of melanoma cells was also significantly inhibited by the oral bombardment of IL-12 cDNA coupled with an irradiated melanoma vaccine administrated to the oral mucosa, compared to treatment with a percutaneous vaccine. IL-12 gene gun therapy, combined with an oral mucosal vaccine, induced interferon-gamma mRNA expression in the host spleen for a long time. These results suggest that immunization of oral mucosa may induce systemic antitumor immunity more efficiently than immunization of the skin and that oral mucosa may be one of the most suitable tissues for cancer gene therapy by means of particle-mediated gene transfer.

Serum and mucosal immune responses to an inactivated influenza virus vaccine induced by epidermal powder immunization

Both circulating and mucosal antibodies are considered important for protection against infection by influenza virus in humans and animals. However, current inactivated vaccines administered by intramuscular injection using a syringe and needle elicit primarily circulating antibodies. In this study, we report that epidermal powder immunization (EPI) via a unique powder delivery system elicits both serum and mucosal antibodies to an inactivated influenza virus vaccine. Serum antibody responses to influenza vaccine following EPI were enhanced by codelivery of cholera toxin (CT), a synthetic oligodeoxynucleotide containing immunostimulatory CpG motifs (CpG DNA), or the combination of these two adjuvants. In addition, secretory immunoglobulin A (sIgA) antibodies were detected in the saliva and mucosal lavages of the small intestine, trachea, and vaginal tract, although the titers were much lower than the IgG titers. The local origin of the sIgA antibodies was further shown by measuring antibodies released from cultured tracheal and small intestinal fragments and by detecting antigen-specific IgA-secreting cells in the lamina propria using ELISPOT assays. EPI with a single dose of influenza vaccine containing CT or CT and CpG DNA conferred complete protection against lethal challenges with an influenza virus isolated 30 years ago, whereas a prime and boost immunizations were required for protection in the absence of an adjuvant. The ability to elicit augmented circulating antibody and mucosal antibody responses makes EPI a promising alternative to needle injection for administering vaccines against influenza and other diseases.

Dendritic cells recruitment and in vivo priming of CD8+ CTL induced by a single topical or transepithelial immunization via the buccal mucosa with measles virus nucleoprotein

The buccal mucosa, a prototype of pluristratified mucosal epithelia, contains a network of directly accessible class II(+) epithelial dendritic cells (DC), similar to skin Langerhans cells. We showed that a single buccal immunization with measles virus nucleoprotein (NP), by either topical application onto or intradermal injection in the buccal mucosa, induced in vivo priming of protective class I-restricted specific CD8(+) CTL. Both routes of immunization with NP induced a rapid recruitment of DC into the mucosa, which peaked at 2 h and decreased by 24 h. Treatment of mice with Flt3 ligand resulted in an increased number of DC in the buccal mucosa and enhanced the frequency of IFN-gamma-producing NP-specific effectors and the NP-specific CTL response generated after buccal immunization with NP. Finally, NP-pulsed bone marrow-derived DC induced NP-specific IFN-gamma-producing cells upon adoptive transfer to naive mice. These data demonstrate that a viral protein delivered to DC of the buccal mucosa induces in vivo priming of protective anti-viral CD8(+) CTL.