Langerhans cells in odontogenic tumours and cysts as detected by S-100 protein immunohistochemistry

Immunohistochemical demonstration of S-100 protein in Langerhans cells (LCs) was made in odontogenic epithelial tumours (71 cases), radicular cysts (40 cases), follicular cysts (28 cases), odontogenic keratocysts (11 cases), primordial cysts (7 cases) and fissual cysts (6 cases). With the use of polyclonal antiserum against S-100 protein, positive LCs, dendrical or irregular in shape were found in tumour or cystic epithelia, and sometimes in stromal connective tissue. Incidence of positive S-100 staining LCs was 11 cases out of 61 ameloblastomas, 22 cases out of 40 radicular cysts, 3 cases of 28 follicular cysts, and other lesions in both odontogenic tumours and cystic diseases lacked LCs. The cases with S-100 protein positive LCs were usually accompanied with a high degree of inflammatory infiltration in their lesions; on the contrary, the negative cases also generally lacked inflammatory responses.     

Collagenase-3 expression in periapical lesions: an immunohistochemical study

Collagenase-3 (matrix metalloproteinase-13) is a metalloproteinase (MMP) that is associated with bone lesions and exhibits variable expression patterns in odontogenic cysts; it may play a role in regulating focal proliferation and maturation of jaw cyst epithelium. We studied the localization, staining intensity and distribution of collagenase-3 in 13 periapical granulomas with epithelium, 16 periapical granulomas without epithelium and 10 radicular cysts using archived formalin fixed, paraffin embedded tissues. A monoclonal antibody against human collagenase-3 was used to evaluate its expression. Immunohistochemical staining intensities of collagenase-3 in all periapical lesions were (?), 4 (10%); (+), 1 (3%); (++), 22 (56%) and (+++), 12 (31%); differences were not statistically significant. Immunohistochemical distribution of collagenase-3 in epithelial cells was (?), 17 (44%); (+), 17 (44%); (++), 5 (13%); in fibroblasts it was (?), 8 (20%); (+), 23 (59%); (++), 8 (21%); in plasma cells it was (?), 7 (18%); (+), 22 (56%); (++), 10 (26%); in macrophages it was (?), 7 (18%); (+), and 15 (38%); and (++), 17 (44%). Statistically significant differences were found in epithelial cells (p = 0.00) and fibroblasts (p = 0.02), whereas differences were not statistically significant for plasma cells and macrophages. Collagenase-3 may play a role in the conversion of a periapical granuloma with epithelium to radicular cyst. MMP's influence not only epithelial rest cell migration, but also invasion of various stromal cells into granulomatous tissue.     

Toll-Like Receptor 4 Expression in the Epithelium of Inflammatory Periapical Lesions.: An immunohistochemical study

Toll-like receptors (TLR) are essential for the innate immune response against invading pathogens and have been described in immunocompetent cells of areas affected by periapical disease. Besides initiating the inflammatory response, they also directly regulate epithelial cell proliferation and survival in a variety of settings. This study evaluates the in situ expression of TLR4 in periapical granulomas (PG) and radicular cysts, focusing on the epithelial compartment.Twenty-one periapical cysts (PC) and 10 PG were analyzed; 7 dentigerous non-inflamed follicular cyst (DC) served as control. TLR4 expression was assessed by immunohistochemistry. TLR4 immunoreaction products were detected in the epithelium of all specimens, with a higher percentage of immunostained cells in PG. Although TLR4 overexpression was detected in both PG and PC, there were differences that seemed to be related to the nature of the lesion, since in PG all epithelial cells of strands, islands and trabeculae were strongly immunoreactive for TLR4, whereas in PC only some areas of the basal and suprabasal epithelial layers were immunostained. This staining pattern is consistent with the action of TLR4: in PG it could promote formation of epithelial cell rests of Malassez and in epithelial strands and islands the enhancement of cell survival, proliferation and migration, whereas in PC TLR4 could protect the lining epithelium from extensive apoptosis. These findings go some way towards answering the intriguing question of why many epithelial strands or islands in PG and the lining epithelium of apical cysts regress after non-surgical endodontic therapy, and suggest that TLR4 plays a key role in the pathobiology of the inflammatory process related to periapical disease.Key words: TLR4, periapical inflammatory granulomas, radicular cysts     

Accumulation of CD1a-positive Langerhans cells and mast cells in actinic cheilitis

LCs and MCs are known to be directly influenced by UV radiation. This study investigated the presence of Langerhans cells (LCs) and mast cells (MCs) in actinic cheilitis (AC) exhibiting epithelial dysplasia (ED). Using immunohistochemistry for CD1a and mast cell tryptase, LCs and MCs density was assessed in 35 cases of AC with different degrees of ED. LCs were found in 32 cases of AC whereas MCs were found in all cases. There was an increase in LCs density irrespective of degree of ED when the cases were compared to normal lip mucosa (P = 0.04343). No statistical difference in LCs density was observed regarding the different degrees of dysplasia (P > 0.05). Significant difference in MCs density between mild and moderate dysplasia and normal lip mucosa was found (P < 0.05). No significant correlation between LCs and MCs was seen (P = 0.1258). Although no correlation could be established between LCs and MCs and the different degrees of ED; it is possible that the accumulation of LCs plays an immunostimulatory and protective role in the defense against progression of dysplasia. Further studies are necessary to determine the role of MCs in the development of AC.     

Down-regulation of Toll-like receptor expression in monocyte-derived Langerhans cell-like cells: implications of low-responsiveness to bacterial components in the epidermal Langerhans cells

In the skin, there are unique dendritic cells called Langerhans cells, however, it remains unclear why this particular type of dendritic cell resides in the epidermis. Langerhans cell-like dendritic cells (LCs) can be generated from CD14(+) monocytes in the presence of GM-CSF, IL-4, and TGF-beta1. We compared LCs with monocyte-derived dendritic cells (DCs) generated from CD14(+) monocytes in the presence of GM-CSF and IL-4 and examined the effect of exposure to two distinct bacterial stimuli via Toll-like receptors (TLRs), such as peptidoglycan (PGN) and lipopolysaccharide (LPS) on LCs and DCs. Although stimulation with both ligands induced a marked up-regulation of CD83 expression on DCs, PGN but not LPS elicited up-regulation of expression CD83 on LCs. Consistent with these results, TLR2 and TLR4 were expressed on DCs, whereas only TLR2 was weakly detected on LCs. These findings suggest the actual feature of epidermal Langerhans cells with low-responsiveness to skin commensals.     

Immunohistochemical characterization and distribution of Langerhans cells in normal epithelium of the uterine cervix

Langerhans cells (LCs) were shown up in normal cervical tissue obtained from 32 women whose age ranged from 25 to 68 years, using immunohistological methods. LCs were detected in metaplastic and native squamous epithelium of the cervix; they were positive to Dako-LC and OKDR antibodies and those located in the basal-suprabasal epithelial layers were also OKT6-positive. The density of the LCs was higher during the proliferative phase of the menstrual cycle. The investigation into the lymphocytes present in the stroma and in the squamous epithelium showed a population of T-lymphocytes identified as predominantly T-cytotoxic/suppressor cells, sometimes in contact with LCs. The significance of these findings is discussed.     

Activated CD34-derived Langerhans cells mediate transinfection with human immunodeficiency virus

Langerhans cells (LCs) are a subset of dendritic cells (DCs) that reside within epidermal and mucosal tissue. Because of their location, LCs are potentially the first cells to encounter human immunodeficiency virus (HIV) during sexual transmission. We report that LCs purified from CD34(+)-derived DCs can facilitate the transinfection of target cells but only after activation. Virions were observed in an intracellular compartment that contains several tetraspanins, in addition to the unique LC markers langerin and CD1a. This reveals that the trafficking of HIV within LCs is reminiscent of that which occurs in mature monocyte-derived DCs and that it varies with the activation state of the cell. The observation that activated LCs can mediate transinfection suggests a potential role for these cells in the known increase in HIV transmission associated with sexually transmitted infections that would cause inflammation of the genital lining.     

Ontogeny of Langerhans cells in human embryonic and fetal skin: cell densities and phenotypic expression relative to epidermal growth

Langerhans cells (LCs) positive for HLA-DR antigens were present in developing human epidermis by at least 7 weeks estimated gestational age (EGA). Most were negative for CD1 (T6) until 12-13 weeks EGA when they underwent a dramatic increase in CD1 reactivity. To gain insight into the density of LCs during ontogeny and to assess whether their distribution was coordinated with epidermal growth, the number of cells positive for both HLA-DR and CD1 antigens was determined relative to surface area and to volume of developing, interfollicular epidermis. LCs differed in their phenotype, distribution (follicular vs. interfollicular), size, and shape between 7 and 21 weeks EGA; however, during this period they maintained a statistically equivalent (P greater than .25) density (65 cells/mm2 and 1,750/mm3) even though the epidermis increased in thickness and the fetus rapidly expanded its surface area. While LCs were evenly distributed within the epidermal sheets at all gestational ages, those in embryonic skin were much smaller and less dendritic than the older cells. The density, size, and shape of LCs in developing skin seemed to be independent of epidermal status (e.g., thickness of keratinization, and number of cell layers) but rather were correlated with gestational age. The number of fetal LCs, through at least 23 weeks EGA, was only 10-20% of the adult LC density. Thus, we can conclude that the increase in LC density to adult levels must occur either during the third trimester or after birth.     

Burn injury suppresses human dermal dendritic cell and Langerhans cell function

Human skin contains epidermal Langerhans cells (LCs) and dermal dendritic cells (DCs) that are key players in induction of adaptive immunity upon infection. After major burn injury, suppressed adaptive immunity has been observed in patients. Here we demonstrate that burn injury affects adaptive immunity by altering both epidermal LC and dermal DC functions. We developed a human ex vivo burn injury model to study the function of DCs in thermally injured skin. No differences were observed in the capacity of both LCs and dermal DCs to migrate out of burned skin compared to unburned skin. Similarly, expression levels of co-stimulatory molecules were unaltered. Notably, we observed a strong reduction of T cell activation induced by antigen presenting cell (APC) subsets that migrated from burned skin through soluble burn factors. Further analyses demonstrated that both epidermal LCs and dermal DCs have a decreased T cell stimulatory capacity after burn injury. Restoring the T cell stimulatory capacity of DC subsets might improve tissue regeneration in patients with burn wounds.     

Nuclear morphometric features of epithelial cells lining keratocysts

OBJECTIVE: To investigate the nuclear morphometric features of epithelial cells lining keratocysts and some other odontogenic cysts. STUDY DESIGN: All cases were selected from the archives of the Department of Pathology, Gülhane Military Medical Academy, as follows: 20 keratocysts and 10 dentigerous and 10 radicular cysts. Nuclear morphometric variables were measured on hematoxylin and eosin-stained histologic slides. Basal and intermediate cells of the epithelium were evaluated separately. Nuclei of the cells were outlined interactively and measured using a specially written macro program. Area, feret ratio (ratio of the longest nuclear axis to the shortest one) and circularity (F circle) of the nuclei were calculated. Additionally, nuclear densitometric analysis was performed on the keratocyst cases. RESULTS: The number of cells in the basal layer (cell density) was higher in keratocysts than in other cysts. The mean nuclear area of basal cells was smaller than of intermediate cells in both keratocysts and other cysts (P < .001). The feret ratio values revealed that basal cell nuclei of keratocysts were more ovoid as compared to those of other cysts (P < .001). Nuclear densitometric findings showed that the DNA indices of all keratocyst cases were close to 1.0, and the cells were considered diploid. CONCLUSION: Increased cell density, a more ovoid nuclear shape and more variation in the size of basal layer cell nuclei in keratocysts were helpful in differentiating these lesions from other odontogenic cysts.     

Loss of TLR2, TLR4, and TLR5 on Langerhans cells abolishes bacterial recognition

It is unknown whether closely related epidermal dendritic cells, Langerhans cells (LCs), and dermal dendritic cells (DDCs) have unique functions. In this study, we show that human DDCs have a broad TLR expression profile, whereas human LCs have a selective impaired expression of cell surface TLR2, TLR4, and TLR5, all involved in bacterial recognition. This distinct TLR expression profile is acquired during the TGF-beta1-driven development of LCs in vitro. Consequently, and in contrast to DDCs, LCs weakly respond to bacterial TLR2, TLR4, and TLR5 ligands in terms of cytokine production and maturation, as well as to whole Gram-positive and Gram-negative bacteria, whereas their responsiveness to viral TLR ligands and viruses is fully active and comparable to DDCs. Unresponsiveness of LCs to bacteria may be a mechanism that contributes to tolerance to bacterial commensals that colonize the skin.     

Lectin-binding patterns in epithelial lining of jaw cysts

Lectin-binding patterns were examined in epithelial walls of 65 jaw cysts (30 post-operative maxillary cysts: POMCs, 20 radicular and 15 follicular cysts), and characteristic lectin staining for each kind of jaw cysts is presented. Between squamous and columnar epithelia, the staining intensity of WGA, Con A and UEA-I was not different, but SBA bound more remarkably to squamous than to columnar epithelia. In both epithelia the outer layers did react more strongly with the lectins examined. Concerning odontogenic cysts, the lectin-binding affinities of outer and intermediate layer cells were nearly the same in both follicular and radicular cysts. Basal cells of radicular cyst walls were however, more markedly positive for lectin binding than of follicular cysts. Furthermore, basal cells of keratinized (RKSE 60 keratin-positive) epithelium were inferior to those of non-keratinized linings in the bindings. Lectin-binding patterns of metaplastic squamose epithelia of POMCs which were positive for RGE53-keratin (principally columnar epithelium-specific keratin) were similar to originally squamous linings of odontogenic cysts. Columnar linings of unusual radicular cysts were positively stained with SBA. By these results, lectin-binding sugar residues of the epithelium seem to be related to the epithelial morphology.     

Relay of Herpes Simplex Virus between Langerhans Cells and Dermal Dendritic Cells in Human Skin

The mechanism by which immunity to Herpes Simplex Virus (HSV) is initiated is not completely defined. HSV initially infects mucosal epidermis prior to entering nerve endings. In mice, epidermal Langerhans cells (LCs) are the first dendritic cells (DCs) to encounter HSV, but it is CD103⁺ dermal DCs that carry viral antigen to lymph nodes for antigen presentation, suggesting DC cross-talk in skin. In this study, we compared topically HSV-1 infected human foreskin explants with biopsies of initial human genital herpes lesions to show LCs are initially infected then emigrate into the dermis. Here, LCs bearing markers of maturation and apoptosis formed large cell clusters with BDCA3⁺ dermal DCs (thought to be equivalent to murine CD103⁺ dermal DCs) and DC-SIGN⁺ DCs/macrophages. HSV-expressing LC fragments were observed inside the dermal DCs/macrophages and the BDCA3⁺ dermal DCs had up-regulated a damaged cell uptake receptor CLEC9A. No other infected epidermal cells interacted with dermal DCs. Correspondingly, LCs isolated from human skin and infected with HSV-1 in vitro also underwent apoptosis and were taken up by similarly isolated BDCA3⁺ dermal DCs and DC-SIGN⁺ cells. Thus, we conclude a viral antigen relay takes place where HSV infected LCs undergo apoptosis and are taken up by dermal DCs for subsequent antigen presentation. This provides a rationale for targeting these cells with mucosal or perhaps intradermal HSV immunization.     

Increased occurrence of PGP 9.5-immunoreactive epidermal Langerhans cells in rat plantar skin after sciatic nerve injury

This study examines the occurrence and distribution of epidermal dendritic cells (DCs) in cryostate sections from plantar skin in normal rats and in rats with a crush injury or neurotomy and suture of the sciatic nerve. The dendritic cells were visualized with antibodies against protein-gene product 9.5 (PGP 9.5). Counts under the fluorescence microscope showed that the occurrence of dendritic cells is increased and that the proportion of dendritic cells in the basal layer is elevated 3 months after sciatic neurotomy and suture but not after a crush lesion. The countings also revealed that the number of cells is elevated as soon as 1 week after neurotomy and suture. Labelling with specific antibodies showed that the dendritic cells examined represent Langerhans cells (LCs). These observations show that there is a neural influence on the occurrence and distribution of PGP 9.5-immunoreactive epidermal Langerhans cells. Whether this influence is direct or indirect remains to be ascertained.     

Cutting edge: virus selectively primes human langerhans cells for CD70 expression promoting CD8+ T cell responses

The two outermost compartments of skin are populated by different Ag-presenting dendritic cell types. Epidermal Langerhans cells (LCs) are evolutionarily adapted to the continuous presence of harmless skin commensals by the selective lack of cell surface TLRs that sense bacteria. In this article, we analyze the ability of LCs and dermal dendritic cells (DDCs) to respond to virus infection. Live virus and intracellular TLR3-agonist dsRNA commit LCs more effectively than DDCs to stimulate naive CD8(+) T cell expansion and their differentiation into effector cells. This potent CD8(+) T cell-promoting capacity of LCs is causally related to high levels of virus-induced CD70 expression but not to IL-12 production. These data suggest a remarkable specialization of LCs in the induction of pathogen class-specific adaptive immunity. Whereas LCs ignore bacteria, they are superior to DDCs to initiate effective CD70-mediated CD8(+) T cells in response to virus stimulation.     

Polyclonal T-Cells Express CD1a in Langerhans Cell Histiocytosis (LCH) Lesions

Langerhans cell histiocytosis (LCH) is a complex and poorly understood disorder that has characteristics of both inflammatory and neoplastic disease. By using eight-colour flow cytometry, we have identified a previously unreported population of CD1a⁺/CD3⁺ T-cells in LCH lesions. The expression of CD1a is regarded as a hallmark of this disease; however, it has always been presumed that it was only expressed by pathogenic Langerhans cells (LCs). We have now detected CD1a expression by a range of T-cell subsets within all of the LCH lesions that were examined, establishing that CD1a expression in these lesions is no longer restricted to pathogenic LCs. The presence of CD1a⁺ T-cells in all of the LCH lesions that we have studied to date warrants further investigation into their biological function to determine whether these cells are important in the pathogenesis of LCH.     

Regulation of immune activity by mild (fever-range) whole body hyperthermia: effects on epidermal Langerhans cells

Inflammation of the skin and systemic fever, both of which occur with injury or infection, include a hyperthermic component that many believe constitutes a physiological stress. Such increases in local or systemic body temperature may also have a regulatory effect on immune function. Langerhans cells (LCs), the dendritic cells of the skin, continuously monitor the extracellular matrix of the skin by taking up particles and microbes that they then carry to draining lymph nodes for presentation to T lymphocytes. We hypothesize that the thermal element of inflammation and/or fever may help regulate the activation and migration of LCs out of the epidermis. To test this hypothesis, Balb/ c mice were exposed to a mild (39.8 degrees C +/- 0.2 degrees C), long-duration (6 hours) whole body hyperthermia (WBH) treatment, which mimics the thermal component of fever. The number of LCs and their morphology were analyzed at various time points up to 7 days after the initiation of WBH. The LCs of the ear epidermis were visualized using a fluorescein isothiocyanate-conjugated antibody specific for the major histocompatibility complex (MHC) class II molecule and confocal microscopy. Although MHC class II staining was diffuse on the surface of the LC body and dendritic extensions of both WBH and control samples, the WBH-treated LCs exhibited a more punctate morphology with fewer dendritic processes compared with control LCs. A significant decrease in the number of LCs was also observed 1 to 5 days after WBH treatment. Furthermore, in vitro heating of Balb/c ear skin cultures at 40 degrees C for 6 to 8 hours enhanced the numbers of viable LCs that migrated into the culture wells. These results suggest that WBH treatment stimulates epidermal LCs in the absence of foreign antigen.     

Langerhans cells and T lymphocyte subsets in the murine vagina and cervix

Immunization in the vagina can lead to the production of specific antibodies in the luminal fluid of this organ. To help understand the immune mechanisms involved in this process, we have studied the occurrence of Langerhans cells (LCs), macrophages, natural killer cells, and T and B lymphocytes in the murine vagina and cervix during the estrous cycle. LCs in the epithelia expressed Ia, F4/80, NLDC-145, and CD45, but not Mac-1, Moma-1, and Moma-2; double-labeling demonstrated phenotypic heterogeneity in this population Ia+, NLDC-145+; Ia+, NLDC-145-; Ia+, F4/80+; Ia+, F4/80-; Ia- F4/80+. T lymphocytes of both helper and cytotoxic/suppressor types were also present in the epithelia, sometimes in close association with LCs, but natural killer cells were not observed. The stroma of the vagina and cervix contained LCs (or interdigitating cells) and macrophages but few T lymphocytes and no B lymphocytes, natural killer cells, or lymphoid nodules. These observations confirm and extend previous reports that the murine vagina and cervix contain epithelial LCs and T lymphocytes and support the suggestion that antigens in the vagina and cervix, as in the epidermis, may be recognized and presented to the immune system by epithelial LCs. However, the paucity of T cells and the absence of B cells and lymphoid nodules from the stroma suggest that antigen presentation may not occur locally but at another site such as in the draining lymph nodes.     

IgE-mediated mast cell activation induces Langerhans cell migration in vivo

Langerhans cells and mast cells are both resident in large numbers in the skin and act as sentinel cells in host defense. The ability of mast cells to induce Langerhans cell migration from the skin to the draining lymph node in vivo was examined. Genetically mast cell-deficient (W/Wv) mice and control mice were sensitized with IgE Ab in the ear pinna. Seven to 14 days later, mice were challenged with Ag i.v. After a further 18-24 h, epidermal sheets and draining auricular lymph nodes were examined using Langerin/CD207 immunostaining. In mast cell-containing mice, a significant decrease in the number of Langerhans cells was observed at epidermal sites of mast cell activation. A significant increase in total cellularity and accumulation of Langerin-positive dendritic cells was observed in the auricular lymph nodes, draining the sites of IgE-mediated mast cell activation. These changes were not observed in W/Wv mice, but were restored by local mast cell reconstitution. Treatment of mast cell-containing mice with the H2 receptor antagonist cimetidine significantly inhibited the observed IgE/Ag-induced changes in Langerhans cell location. In contrast, Langerhans cell migration in response to LPS challenge was not mast cell dependent. These data directly demonstrate the ability of mast cells to induce dendritic cell migration to lymph nodes following IgE-mediated activation in vivo by a histamine-dependent mechanism.     

Langerhans cells that have matured in vivo in the absence of T cells are fully capable of inducing a helper CD4 as well as a cytotoxic CD8 response

Langerhans cells (LCs) are immature dendritic cells (DCs) present in the skin epithelium. Upon Ag exposure, they migrate to the draining lymph nodes where they mature into potent stimulators of naive T cells. The aim of this study was to investigate the influence of T cells on LC migration and maturation. Therefore, the in vivo migration and maturation of LCs after sensitization with the hapten FITC was compared between C57BL/6 or BALB/c mice used as positive controls, and recombination activating gene (RAG) 1 knockout (-/-) mice or SCID mice used as T cell-deficient mice. Phenotypically, there was no difference between migrated LCs from RAG1-/- or SCID mice vs normal C57BL/6 or BALB/c mice: both populations of FITC+ cells had a dendritic morphology and a mature phenotype as they expressed high levels of MHC class II molecules and costimulatory molecules CD80, CD86, and CD54. Sorted migrated LCs of RAG1-/- or SCID mice were efficient stimulators of allogeneic T cells and Ag-specific CD4+ T cells. The same results were found if migrated LCs were fixed instead of irradiated, excluding the possibility that LCs derived from RAG1-/- or SCID mice would mature in the presence of T cells during the stimulation tests. Importantly, fixed migrated LCs of RAG1-/- mice were also efficient stimulators of cytotoxic CD8+ T cells. These data suggest that T cells are not required for full maturation of LCs.