A model implicating the Langerhans cell in keratinocyte proliferation control

Topical drug delivery strategies for enhancing drug effectiveness by skin barriers, drug delivery systems and individualized dosing

Topical drug delivery is widely used in various diseases because of the advantages of not passing through the gastrointestinal tract, avoiding gastrointestinal irritation and hepatic first-pass effect, and reaching the lesion directly to reduce unnecessary adverse reactions. The skin helps the organism to defend itself against a huge majority of external aggressions and is one of the most important lines of defense of the body. However, the skin's strong barrier ability is also a huge obstacle to the effectiveness of topical medications. Allowing the bioactive, composition in a drug to pass through the stratum corneum barrier as needed to reach the target site is the most essential need for the bioactive, composition to exert its therapeutic effect. The state of the skin barrier, the choice of delivery system for the bioactive, composition, and individualized disease detection and dosing planning influence the effectiveness of topical medications. Nowadays, enhancing transdermal absorption of topically applied drugs is the hottest research area. However, enhancing transdermal absorption of drugs is not the first choice to improve the effectiveness of all drugs. Excessive transdermal absorption enhances topical drug accumulation at non-target sites and the occurrence of adverse reactions. This paper introduces topical drug delivery strategies to improve drug effectiveness from three perspectives: skin barrier, drug delivery system and individualized drug delivery, describes the current status and shortcomings of topical drug research, and provides new directions and ideas for topical drug research.

Effect of chronic ethanol ingestion on dendritic cell population during oral mucosal repair: An experimental study

The aim of this study was to analyze the effect of chronic ethanol ingestion on dendritic cell repopulation during the repair process of rat oral mucosa and in the rat spleen by analyzing the immunohistochemical expression of dendritic cell markers. Wistar rats ingested 20% ethanol solution for 28 days; a surgical wound was performed on the rat tongue after this period. The repair process and the number of CD1a+, CD11c+, and CD207+ cells in the regions adjacent to the wound were determined at day 1, 3, and 7 following the wound as well as in the rat spleen. The wound-only group (no ethanol exposure) had complete reepithelization after 7 days, but this did not occur in the ethanol + wound group at this time point. The inflammatory infiltrate was significantly reduced in animals exposed to ethanol, which also showed significantly lower counts of CD1a+, CD11c+, and CD207+ cells than the wound-only group at all experimental time points. In addition, ethanol exposure also resulted in lower densities of CD11c+ and CD207+ cells in the rat spleen. In conclusion, chronic ethanol intake had a negative impact on dendritic cell numbers, a fact that may contribute to delay in oral mucosa repair.

The Potentials and Pitfalls of a Human Cervical Organoid Model Including Langerhans Cells

Three-dimensional cell culturing to capture a life-like experimental environment has become a versatile tool for basic and clinical research. Mucosal and skin tissues can be grown as “organoids” in a petri dish and serve a wide variety of research questions. Here, we report our experience with human cervical organoids which could also include an immune component, e.g., Langerhans cells. We employ commercially available human cervical keratinocytes and fibroblasts as well as a myeloid cell line matured and purified into langerin-positive Langerhans cells. These are then seeded on a layer of keratinocytes with underlying dermal equivalent. Using about 10-fold more than the reported number in healthy cervical tissue (1–3%), we obtain differentiated cervical epithelium after 14 days with ~1% being Langerhans cells. We provide a detailed protocol for interested researchers to apply the described “aseptic” organoid model for all sorts of investigations—with or without Langerhans cells.

Depletion of langerin+ cells enhances cutaneous wound healing

Langerin is a C-type lectin receptor that is expressed on Langerhans cells and langerin-positive dermal dendritic cells in the skin. Little is known about the function of langerin⁺ cells in wound healing. In this study, the effects of ablation of langerin⁺ cells on healing of a full-thickness excision wound were investigated using the langerin-DTR depletable mouse. Strikingly, depletion of langerin⁺ cells resulted in more rapid reduction in wound area. Accelerated wound healing in the langerin⁺ -cell-depleted group was characterized by enhanced neo-epidermis and granulation tissue formation, and increased cellular proliferation within the newly formed tissues. Accelerated healing in the absence of langerin⁺ cells was associated with increased levels of granulocyte-macrophage colony-stimulating factor, F4/80⁺ cells and blood vessels within the granulation tissue. These data support an inhibitory role for langerin⁺ cells during wound healing. Therapies that suppress langerin⁺ cells or their function may therefore have utility in progressing the healing of wounds in humans.

Of skin and bone: did Langerhans cells and osteoclasts evolve from a common ancestor?

Skin Langerhans cells are antigen-presenting cells of the interfollicular epidermis and the upper part of the hair follicle, whereas osteoclasts are specialized bone-resorbing macrophages. Although at first view these two cell types appear to have little in common, a closer analysis reveals shared features, and when taking into account their surrounding environment, a hypothesis can be developed that Langerhans cells and osteoclasts have evolved from a common ancestral cell type. In this mini-review, we have compared the ontogenetic features of Langerhans cells and osteoclasts from a genetic and a functional point of view, an issue that so far has been overlooked. The gene programs that control cell differentiation, and the body parts where they reside, present surprising similarities. Whereas the function of osteoclasts in bone degradation has been established since the first vertebrates, Langerhans cells may have undergone a stepwise adaptation from aquatic to terrestrial life. Their cell function co-evolved with the imperatives of the skin to protect against physical impact, heat, water loss and pathogens, which implied the capacity of Langerhans cells to associate with skin appendages and to develop immunostimulatory functions. For the highly versatile and efficient immune system of modern vertebrates, Langerhans cells may be a memory of the past.

Increased number of Langerhans cells in the epidermis of diabetic foot ulcers correlates with healing outcome

Langerhans cells (LCs) are a specialized subset of epidermal dendritic cells. They represent one of the first cells of immunologic barrier and play an important role during the inflammatory phase of acute wound healing. Despite considerable progress in our understanding of the immunopathology of diabetes mellitus and its associated comorbidities such as diabetic foot ulcers (DFUs), considerable gaps in our knowledge exist. In this study, we utilized the human ex vivo wound model and confirmed the increased epidermal LCs at wound edges during early phases of wound healing. Next, we aimed to determine differences in quantity of LCs between normal human and diabetic foot skin and to learn if the presence of LCs correlates with the healing outcome in DFUs. We utilized immunofluorescence to detect CD207+ LCs in specimens from normal and diabetic foot skin and DFU wound edges. Specimens from DFUs were collected at the initial visit and 4 weeks later at the time when the healing outcome was determined. DFUs that decreased in size by >50 % were considered to be healing, while DFUs with a size reduction of <50 % were considered non-healing. Quantitative assessment of LCs showed a higher number of LCs in healing when compared to non-healing DFU's. Our findings provide evidence that LCs are present in higher number in diabetic feet than normal foot skin. Healing DFUs show a higher number of LCs compared to non-healing DFUs. These findings indicate that the epidermal immune barrier plays an important role in the DFU healing outcome and may offer new therapeutic avenues targeting LC in non-healing DFUs.

Epithelial stem cells

It is likely that adult epithelial stem cells will be useful in the treatment of diseases, such as ectodermal dysplasias, monilethrix, Netherton syndrome, Menkes disease, hereditary epidermolysis bullosa, and alopecias. Additionally, other skin problems such as burn wounds, chronic wounds, and ulcers will benefit from stem cell-related therapies. However, there are many questions that need to be answered before this goal can be realized. The most important of these questions is what regulates the adhesion of stem cells to the niche versus migration to the site of injury. We have started to identify the mechanisms involved in this decision-making process.

Differentiation and heterogeneity in the mononuclear phagocyte system

Cells of the mononuclear phagocyte system (MPS) are found in large numbers in every organ of the body, where they contribute to innate and acquired immunity and homeostasis. This review considers the locations of MPS cells, surface markers that distinguish subsets of monocytes and macrophages, the pathways of MPS differentiation, and the growth factors and transcription factors that guide them. Although the number of MPS sub-populations that can be defined is infinite, the features that unite the MPS remain compelling. Those features clearly include antigen-presenting dendritic cells within the MPS and argue against any basis for separating them from macrophages.

Immunohistochemical analysis of CD1a-labeled Langerhans cells in human dental periapical inflammatory lesions--correlation with inflammatory cells and epithelial cells

OBJECTIVE

Distribution and density of CD1a-labeled Langerhans cells (LCs) were examined in human dental periapical inflammatory lesions, and compared with inflammatory cell infiltration or epithelial cell proliferation.

MATERIALS AND METHODS

Eighty three periapical lesions (26 apical granulomas (AGs), 8 epitheliated granulomas (EGs), 34 radicular cysts (RCs), 15 residual radicular cysts (RRCs)) were collected. As control, specimens of periodontal ligaments including Malassez epithelial rests were curetted from 21 teeth. LC densities were measured and various degrees of inflammatory cell infiltration were examined immunohistochemically. Labeling indices for the cellular proliferation markers Ki-67 antigen and DNA topoisomerase II alpha were calculated in the epithelial components.

RESULTS

LCs were found in all periapical lesions but not in Malassez epithelial rests. LCs were more abundant in epithelial components than in subepithelial layers. Intraepithelial LCs were more frequent in RCs than in RRCs, whereas subepithelial LCs were less frequent in RRCs than in AGs and EGs. T lymphocytes consistently outnumbered macrophages, plasma cells and B lymphocytes. The range of the CD4/CD8-positive cell ratio differed according to the lesions. Increased LC density was associated with the severity of CD3-positive cell infiltration. Ki-67- and Topo II-LI showed various degrees of epithelial immunoreactivity. There was a significant correlation between LC density and proliferative potential of the epithelium in periapical lesions.

CONCLUSION

These findings suggested that LCs appeared to be associated with T lymphocyte infiltration and proliferative potential of the epithelial tissue in periapical lesions.

A strikingly constant ratio exists between Langerhans cells and other epidermal cells in human skin. A stereologic study using the optical disector method and the confocal laser scanning microscope

Langerhans cells play an important part in the immune surveillance of the human epidermis. Therefore, a certain distribution and numerical relationship to other epidermal cells can be expected. To quantify epidermal Langerhans cells population extensive studies have been performed using two-dimensional quantification methods on vertical sections or epidermal sheet preparations. Whereas methods using vertical sections were complicated considerably by the sampling procedure, the dendritic shape, and the suprabasal, nonrandom distribution of Langerhans cells, epidermal sheet preparations have their limitations regarding the numerical relationship of Langerhans cells to total epidermal cells and the epidermal morphology as such. In order to improve the validity of data the three-dimensional dissector method combined with confocal laser scanning microscopy has been applied to quantify the number of Langerhans cells and other epidermal cell nuclei per volume unit in cryosections of 24 punch biopsies of normal breast skin of eight women. Furthermore, the ratio of Langerhans cells to other epidermal cells, their number per biopsy, and per skin surface area were calculated. To minimize the bias by shrinkage the reference volume was estimated using Cavalieri's principle. A constant ratio of one Langerhans cells to 53 other epidermal cells was identified in breast skin (interindividual correlation coefficient: 0.952, p < 0.0001). Thus, Langerhans cells represent 1.86% of all epidermal cells; however, a wide interindividual range was found for the number of Langerhans cells per mm2 (912-1806; mean +/- SD 1394 +/- 321) and other epidermal cells per mm2 (47,315-104,588; mean +/- SD 73,952 +/- 19,426). This explains the conflicting results achieved by conventional morphometric assessments relating cell numbers to skin surface area, ignoring the varying thickness of the epidermis. The surprisingly constant relationship of Langerhans cells to other epidermal cells stresses the hypothesis of an epidermal Langerhans cells unit where one Langerhans cells seems to be responsible for the immune surveillance of 53 epidermal cells.

beta-Endorphin binding and regulation of cytokine expression in Langerhans cells

Neuropeptides and neurohormones have been shown to be able to regulate cutaneous immune reactions. Binding of beta-endorphin (beta-end) on epidermal Langerhans cells (LC) and effects of beta-end on cytokine expression were examined. Biotinylated beta-end bound to the mouse LC-like cell line, XS52, and the binding was replaced with intact beta-end but not with substance P. beta-End augmented secretion of IL-1 beta and IL-10 from XS52 cells were induced by a combination of LPS and GM-CSF. Induction of TNF alpha was suppressed by beta-end. The regulation of cytokine expression was confirmed in fresh LC by RT-PCR. These results suggest that beta-end is a regulator of skin immune function.

Hemopoietic stem cell inhibitor (SCI/MIP-1 alpha) also inhibits clonogenic epidermal keratinocyte proliferation

The maintenance and regulation of continuously renewing tissues is ultimately controlled at the level of stem-cell proliferation. We have recently identified a reversible inhibitor of hemopoietic stem-cell proliferation (stem-cell inhibitor [SCI]), which is identical to the macrophage inflammatory protein, MIP-1 alpha, a 69-amino-acid heparin-binding cytokine. To test the cell/tissue specificity of the inhibition of proliferation by SCI/MIP-1 alpha, we have investigated its activity on epidermal keratinocytes, the principal cell type of another continuously renewing tissue. Here we show that SCI/MIP-1 alpha inhibits the proliferation of epidermal keratinocytes in vitro and that the MIP-1 alpha mRNA is present in epidermal Langerhans cells but not in keratinocytes. This suggests an important growth regulatory function for SCI/MIP-1 alpha in keratopoiesis, as well as hemopoiesis, and may also indicate a novel role for the epidermal Langerhans cell. As SCI/MIP-1 alpha can inhibit the proliferation of embryologically distinct precursor cells, this raises the possibility that it may also function in a number of other tissues.

Density and morphology of Langerhans cells in basal cell carcinomas of the face and trunk

We investigated the density and morphology of Langerhans cells in epidermal sheets of basal cell carcinomas in chronically sun-exposed skin (face) and less exposed skin (trunk) of 65 patients. Langerhans cells in perilesional and control skin at the same anatomical sites as the tumours were also examined. Two markers (ATPase and OKT6) were used in a parallel fashion to identify Langerhans cells. The density of the cells was reduced, and their morphology was changed in epidermis overlying tumours of both the face and trunk. These alterations were confined to tumour areas, as Langerhans cells in perilesional skin were normal when compared with control skin at both anatomical sites. Results with both markers were the same.

Epidermal keratinocyte stem cells: their maintenance and regulation

The epidermis is a stratified epithelium consisting of interfollicular regions and appendages (hair follicles, sweat glands, sebaceous glands). The dominant cell type (the keratinocyte) is arranged in groups of cells termed epidermal proliferative units (EPUs), and one centrally-located clonogenic stem cell is ultimately responsible for replacing the remainder of the cells in the unit. Evidence is reviewed which indicates that the epidermal Langerhans' cell (ELC), and the cells comprising the dermis, may modify the keratinocyte microenvironment to create stem cell 'niches' and cellular diversity within the basal layer.

Activated human Langerhans cells express mRNA for IL-1 alpha and IL-1 beta and produce these cytokines but do not secrete them

Human Langerhans cells (LC) were isolated from epidermal cell preparations by panning with mouse anti-CD1 monoclonal antibody. RNA was prepared and probed for the presence of mRNAs for various cytokines using radiolabeled cDNAs. After stimulation with phorbol myristate acetate LC express RNA for interleukin 1 alpha (IL-1 alpha) and interleukin 1 beta (IL-1 beta) and produce proteins but do not secrete them at detectable levels. LC-associated IL-1, particularly IL-1 alpha, may play a role in antigen presentation. PMA did not induce IL-6 expression in LC. The addition of lipopolysaccharide, a muramyl dipeptide analog, ionomycin, IL-1 alpha, tumor necrosis factor-alpha, insulin-like growth factor-1 or IL-6 did not induce IL-1 mRNA in LC. UVB augmented IL-1 beta mRNA expression. Glucocorticoids did not detectably affect IL-1 alpha or IL-1 beta mRNA levels following PMA induction, however, staurosporin inhibited IL-1 beta mRNA synthesis. Thus the inducers and regulators of IL-1 formation in human LC and monocytes are not identical.

Dynamic nature and function of epidermal Langerhans cells in vivo and in vitro: a review, with emphasis on human Langerhans cells

Epidermal Langerhans cells (LC) are Birbeck granule-containing bone-marrow-derived cells, which are located mainly in the suprabasal layer of the epidermis. They can be readily identified by their strong expression of CD1a and MHC class II molecules. In addition to these 'classical' properties, an extensive phenotypic profile of normal human LC, summarized in this review, is now available. The powerful capacity of LC to activate T lymphocytes is clearly documented and, to date, LC are recognized as the prominent antigen-presenting cells of the skin immune system. They are generally believed to pick up antigens encountered in the epidermis and to migrate subsequently from the epidermis to the skin-draining lymph nodes. Upon arrival in the paracortex of lymph nodes, the antigen-laden LC transform into interdigitating cells and they present antigen to naive T lymphocytes in a MHC class II-restricted fashion; this results in the generation of antigen-specific immune responses. It has also been demonstrated that transformation of LC into interdigitating cells occurs when LC are cultured in vitro. Both in vivo and in vitro studies have indicated that properties of LC, such as phenotype, morphology and the stimulatory potential to activate T lymphocytes, are dependent on the local microenvironment in which the LC reside. The essential role of LC in the induction of contact allergic skin reactions and skin transplant rejection is well established.

Keratoderma hereditaria mutilans. Etretinate treatment and electron microscope studies

Keratoderma hereditaria mutilans is a rare inherited cornification disorder characterized by hyperkeratosis of palms and soles with a characteristic "honey-comb" appearance, keratotic constriction furrows of one or more digits (pseudo-ainhum) and threatening spontaneous amputation. Approximately 30 cases have been reported, but the ultrastructural features have not been well characterized. In this article, we describe the clinical, histologic, and ultrastructural findings in our patient. A biopsy specimen taken before treatment with etretinate showed hyperkeratosis with a well-preserved granular layer and acanthosis. Ultrastructural examination disclosed that the spinous cells and granular cells contained marked swollen mitochondria, many desmosomes, and that corneocytes contained many membrane coating granules (MCG) and lipid like vacuoles. After initiation of treatment, considerable clinical improvement was observed, but without significant histologic modification. The principal post-treatment ultrastructural changes were the reduction of mitochondrial swelling in spinous and granular cells and the reduction in the number of MCG in corneocytes. The intercellular spaces showed increased amounts of fine and coarse granular substances. Stimulation of Langerhans cells was observed. Marginal band formation occurred normally after treatment.

Replacement of Langerhans cells in murine palate

Palates from C3H mice were implanted onto prepared graft beds in histocompatible F1 hybrid mice. Biopsies taken 1, 2, 4, 8, and 16 wk later were prepared to demonstrate Langerhans cells (LC) of C3H and F1 (host) origin. After 1 wk only occasional LC (all of C3H origin) were present. By 2 wk total LC numbers had increased to a level approximately 50% greater than in control (non-implanted) palate, with most of this increase due to C3H LC proliferation. From 4 through 16 wk total LC numbers were not significantly different from those of control palate. During weeks 2 through 16 the percentages of LC of F1 origin were 31, 70, 39, and 19% respectively. These results indicate an increased proliferation of C3H LC with an initial migration of F1 LC which stops as C3H LC numbers increase.

Successful treatment of a patient with Reiter's syndrome and acquired immunodeficiency syndrome using etretinate

In a 30-year-old homosexual man with a 3-year history of localized psoriasis, an oligoarthropathy and severe cutaneous lesions of Reiter's syndrome developed 6 months after acquired immunodeficiency syndrome (AIDS) was diagnosed. Reiter's syndrome and psoriasis may be a continuum of similarly expressed cutaneous diseases that develop in genetically predisposed individuals. We discuss the possible involvement of T lymphocytes and Langerhans cells in the cutaneous lesions of AIDS patients with psoriasis and Reiter's syndrome. In these AIDS patients, skin disease tends to be severe and recalcitrant to conventional therapy. Etretinate plus topical fluorinated steroids was an excellent treatment, producing near clearance of skin lesions and significant improvement in the oligoarthropathy.

Ultrastructural features of Langerhans cells in clinically uninvolved skin of psoriatics

Epidermal Langerhans cells (LC) from skin of clinically normal appearance in psoriatics were studied electron microscopically and compared with LC from the skin of healthy volunteers and from those with other dermatoses. Results show that LC from psoriatics display partly distinct cytoplasmic alterations. Moreover, about half of LC investigated were partly or mainly surrounded by clearly widened intercellular spaces, such that an immediate cellular contact with neighbouring keratinocytes was correspondingly decreased. Whether such LC are functionally altered remains to be clarified.

Alterations in Langerhans cells during growth of transplantable murine tumors

To investigate the response of Langerhans cells to tumor growth, we examined the appearance and number of ATPase+ and Ia+ dendritic cells in the epidermis covering subcutaneous tumors. Mice were injected with cells from syngeneic UVB- and PUVA-induced tumors and a melanoma, and the overlying skin was examined at various times during progressive tumor growth. An increase in the number of ATPase+ and Ia+ dendritic cells was observed in skin over all three tumor types. Morphologic alterations in the cells were also noted, including a decrease in dendricity. These changes were apparent only in skin directly over growing tumor masses; contralateral and perilesional skin was unaffected. Injection of nontumorigenic cells and implantation of silicon did not induce changes in Langerhans cells. Regression of highly antigenic tumor cells and tumor regression in immunized mice were not accompanied by detectable alterations in Langerhans cells, whereas changes in Langerhans cells were apparent during tumor growth in nude mice. These results demonstrate that changes in the number and morphology of Langerhans cells occur in response to tumor growth but that the changes are not dependent on immunologic or inflammatory responses.

Does radiation-induced abrogation of skin Langerhans cell functions lead to enhanced incidence of skin tumors in patients with genetic disorders of DNA repair?

A hypothesis is presented which states that persons with the genetic disorders xeroderma pigmentosum and ataxia-telangiectasia, manifested by a deficiency of DNA repair, develop cutaneous tumors due to the elimination of reticuloendothelial system cells (Langerhans cells) in the skin, and the subsequent loss of control of epidermal cellular elements.

Langerhans cells in molluscum contagiosum, verruca vulgaris, plantar wart, and condyloma acuminatum

To determine a possible role of Langerhans cells in viral infection of skin, we studied the distribution of Langerhans and indeterminate cells in the lesional skin of mollusca contagiosa, verrucae vulgaris, plantar warts, and condylomata acuminata. A total absence of Langerhans and indeterminate cells was observed in molluscum contagiosum, but their number appeared to be normal or increased in the perilesional normal skin. Few Langerhans and indeterminate cells were seen in the suprabasal location in verrucae vulgaris and plantar warts, and normal numbers were noted in the perilesional skin. In contrast, a larger number of Langerhans and indeterminate cells reaching up to stratum granulosum were found in the condylomata acuminata. It is possible that alteration of keratinocytes by viral infection may effect the migration of Langerhans cells to the epidermis. The lack of Langerhans cells may lead to a paucity of inflammatory response (in particular, T cell-mediated response) to the cells infected with the virus.

Histiocytes in nasopharyngeal carcinoma in relation to prognosis

Forty-nine biopsy specimens of nasopharyngeal carcinoma and 20 biopsy specimens of nasopharyngeal mucosa obtained from non-cancer patients were studied for the presence of T-zone histiocytes (Langerhans' cells and their precursors) and macrophages by immunohistochemical methods with the use of antibodies against S-100 protein and lysozyme (lys), respectively. Patients with dense infiltration of T-zone histiocytes in the primary sites survived longer than those without such infiltration (mean survival times, 8, 39, and 72 months in the patients with the density of -, +, and ++, respectively; P less than 0.005). In contrast, there was no relationship between patient prognosis and density of lys+ macrophages in the tumor tissue (P = 0.33). The distribution of T-zone histiocytes in the tumor tissue was different from that of macrophages. T-zone histiocytes may play an important role in the immune reaction against cancer, probably acting through mechanism different from that of macrophages.

The effect of atrophy, hyperplasia, and keratinization accompanying the estrous cycle on Langerhans' cells in mouse vaginal epithelium

The morphology and numbers of Langerhans' cells vary in epithelia with different patterns of hyperplasia and keratinization. Langerhans' cells stained for ATPase were compared at five phases of the estrous cycle in murine vaginal epithelium. The cells were more dendritic and sparsely distributed with hyperplasia and were less dendritic and more densely distributed with atrophy. Greater numbers of the cells did not accompany keratinization at estrus. Ultrastructurally, three types of Langerhans' cells were discriminated. The first type, active in protein synthesis and phagocytosis, was commonest in sloughing and atrophic epithelium. The second type, containing accumulated and dispersed, electron-dense bodies presumed to be lysosomes, predominated in hyperplastic epithelium. The third, a mature resting cell, was found only after keratinization was complete. This study shows that Langerhans' cells in murine vaginal epithelium vary in morphology and numbers with the epithelial changes of the estrous cycle which may relate to their immunological role, but does not support the contention that their distribution is important for keratinization.

Effect of ultraviolet B radiation on S-100 protein antigen in epidermal Langerhans cells

Ultraviolet B (UVB) radiation has been shown to induce significant alterations in both function and surface antigen expression of epidermal Langerhans cells (ELC). In this study we investigated the effect of UVB radiation on ELC marker S-100 protein antigen (S-100 Ag) which is present in the nucleus and cytoplasm of human ELC. A total of 34 sites on 31 volunteers were exposed to 3 MED (minimal erythema dose) of UVB and biopsied at various times up to 7 days after irradiation. Skin from 9 noninjured and 7 slice-wounded subjects served as controls. The avidin-biotin-peroxidase staining technique was used to identify S-100 Ag in sections of formalin-fixed, paraffin-embedded tissue, and the numbers of stained suprabasal dendritic cells were then counted over a 200 basal cell length of interfollicular epidermis. Noninjured skin had 3.56 +/- 3.01 cells, whereas slice-wounded skin had elevated numbers (greater than 10.0 cells) at 1, 24, and 48 h after injury. Following UVB irradiation, a significant (p less than 0.001) increase in antigen-positive cells (14 +/- 3.46) was found at 1 h; this number declined to just below normal at 12 h, but by 48 h returned to and remained at preinjury levels. In contrast to previous observations of the depletion of ELC surface markers by UVB radiation, we demonstrate here that the numbers of S-100 Ag-positive ELC actually increase following comparable doses of radiation. Since this increase occurs so rapidly following both UVB irradiation and slice injury, S-100 Ag may be synthesized or unmasked within the ELC as a response to wounding of the epidermis.

Loss of Langerhans cells from gingival tissue maintained in organ culture

Changes occurring in a population of Langerhans cells (LC) were investigated using human gingival epithelium maintained in organ culture. The enzyme adenosine-5'-triphosphatase together with the surface antigens HLA-DR and T6 were used to identify and quantitate these cells. An exponential fall in the expression of each of these markers was seen to occur with increasing incubation time, suggesting that a true loss of these cells is in fact occurring. HLA-DR antigen is shed from LC at a rate significantly greater than that at which LC are lost. A mathematical model which simulates the behaviour of LC within organ culture is presented, and several implications and possible explanations proposed.

Biology of Langerhans cells: analysis by experiments to deplete Langerhans cells from human skin

In vivo studies have demonstrated that various treatments of skin, e.g., UV irradiation, topical corticosteroids, and tape-stripping, will temporarily deplete the epidermis of Langerhans cells (LC). Whether this loss represents simply a loss of cell surface markers unique to LC, or actual depletion of cells, is unknown. By design, normal human skin transplanted to the congenitally athymic (nude) mouse is a system devoid of circulating precursors for human LC. Because LC have been shown to be of bone marrow origin, any depletion of these cells in this system should be permanent. Treatments to deplete LC from human skin grafts on nude mice after grafting included: (a) large doses of UV radiation (400 mJ/cm2 every 48 h, X 3), (b) potent high-dose topical corticosteroids (2.5 mg betamethasone valerate/cm2 every day, X 5), (c) tape-stripping (X 20). Treatments before grafting included: (a) treating donor skin with 900 R of gamma irradiation, (b) complement fixing monoclonal antibody to Ia-like antigens of LC, followed by fresh complement, (c) monoclonal antibody conjugated to toxins. Quantitation of the number of LC was analyzed on control and treated epidermal sheets using immunodiagnostic reagents, anti-HLA-DR, and surface ectoenzymes , ATPase. Results show that both UV irradiation and topical corticosteroids reduce the number of LC by these analyses. However, within 3 weeks, recovery to pretreatment levels has occurred. X-irradiation and tape-stripping were without effect. Despite evidence that the monoclonal antibody, complement, and toxic systems were delivered to the LC within the epidermis, there is no evidence that these treatments resulted in a decrease in LC. It appears that LC are currently either long-lived or replaced locally from a proliferative pool and that certain cell membrane determinants of human LC are somewhat differentially sensitive to UV radiation and corticosteroids.

Relation of antipsoriatic and Langerhans cell depleting effects of systemic psoralen photochemotherapy: a clinical, enzyme histochemical, and electron microscopic study

The possible relation between the therapeutic action and Langerhans cell (LC) depleting effect of psoralen photochemotherapy (PUVA) was investigated in 9 psoriatic patients by parallel recording of the clinical status, using the psoriasis area and severity index ( PASI ), and the epidermal LC counts of uninvolved skin, using light (ATPase staining) and electron microscopy (EM). Both light and electron microscopically recorded LC numbers decreased significantly during the PUVA course of, on the average, 21 exposures and a mean cumulative UVA dose of 77 J/cm2. At the end of the treatment period, both the PASI score and the light microscopically recorded LC density had reduced to about one-tenth of original, i.e., from 7.5 +/- 5.7 to 0.8 +/- 0.8 points and from 787 +/- 70 to 60 +/- 48 cells/mm2, respectively. After cessation of the PUVA course, the PASI scores remained low during the 3-7 week follow-up period, while the LC counts returned to normal, and even exceeded the starting value by 12%. Although a possible functional impairment of LC in the post-PUVA period cannot be excluded, the data are interpreted as speaking against the hypothesis that the therapeutic action of PUVA would be mediated through its LC effects.

Dynamics of Langerhans cells in genetically defined murine epidermal cell culture

Unlike keratinocytes, Langerhans cells express both surface ATPase activity and Ia (HLA-DR) antigens. A well-characterized in vitro system containing Langerhans cells would be of great use in elucidating their functions. Thus, epidermal cell cultures derived from neonatal Balb/c mice were examined for the presence of Langerhans cells. Twenty-four hours after initiation of culture, ATPase- and Ia-positive cells were seen to be associated with cell aggregates. By day 3, Langerhans cells migrated on to the substratum and, as the cultures matured and stratified, were seen both in groups and as single cells for the duration of the cultures (day 14). During culture, although the total number of cells increased, the percentage of cells expressing Ia antigen and ATPase activity remained constant, suggesting that Langerhans cells increase in number during cell culture. Such a situation could arise from actual division of Langerhans cells during culture or from latent expression of Ia antigen and ATPase activity by pre-existing cells. This is the first study of the dynamics of Langerhans cells in a cell culture system and shows that Langerhans cells are present throughout the lifespan of the cultures.

Langerhans cells in autosomal dominant ichthyosis vulgaris

Five patients with autosomal dominant ichthyosis vulgaris (ADI) were studied to see whether the abnormal keratinization was associated with disturbances of the appearance or the distribution of epidermal Langerhans cells (LCs). The LCs were identified by ATPase staining and electron microscopy. They were present in normal numbers, were of normal morphology and were in their usual mid-epidermal position. These observations do not support the hypothesis that LCs are involved directly in the process of keratinization.

Langerhans cells in skin from patients with psoriasis: quantitative and qualitative study of T6 and HLA-DR antigen-expressing cells and changes with aromatic retinoid administration

Using a monoclonal antibody against human HLA-DR antigens and OKT6, we investigated by indirect immunofluorescence the distribution of Langerhans cells in normal human skin and involved and uninvolved skin from patients with psoriasis before, during, and after systemic aromatic retinoid administration. In parallel, enumeration of HLA-DR and of OKT6+ cells was also performed. In involved psoriatic epidermis the distribution of positive cells was disturbed; OKT6+ cells were reduced in number, as were HLA-DR+ cells which were seen in clusters. In control skin sections, a regular pattern of fluorescent dendritic epidermal cells was noted. In normal-appearing human skin, in nonlesional psoriatic skin, but not in diseased psoriatic skin, the number of OKT6+ cells per epidermal section surface unit was higher than that of HLA-DR expressing cells. Changes in the number and distribution of OKT6 and HLA-DR+ cells in psoriatic involved epidermis were corrected by oral retinoid treatment.

Biology of Langerhans cells: selective migration of Langerhans cells into allogeneic and xenogeneic grafts on nude mice

A major question challenging immunobiologists relates to those mechanisms that control the selective movement of cells involved in immune and inflammatory processes at various tissue sites such as the skin. Little is known about those influences that control the selective migration of macrophage-like Langerhans cells (LC) to normal epidermis, where it is uniformly distributed. Mechanistically, this includes the interaction of blood-borne LC precursors with the vascular endothelium of the skin and those factors that control the migration of the LC into the avascular epidermal component of the skin. By using (i) monoclonal antibodies specific for I-region associated Ia antigens found on LC from various inbred strains of animals and (ii) the congenitally athymic (nude) mouse as an immunologically compromised recipient of allografts and selected xenografts, we developed a model system to study the factors that restrict LC migration into the epidermis. Using this model, which excludes the need to lethally x-irradiate graft recipients, we established that: (i) the ingress of LC does not show major histocompatibility complex restriction [LC of the nude host are capable of migrating into the epidermis of allogeneic and certain xenogeneic (rat) skin grafts]; (ii) host LC are incapable of migrating into the epidermis of guinea pig or human skin grafts; (iii) the ingress of host LC into the epidermis of the graft is not accompanied by an overgrowth of the graft by host epidermis; and (iv) LC or LC precursors are capable of dividing in the skin or, alternatively, represent an extremely long-lived cell population. The specificity of this model system provides a powerful tool to help understand many aspects of LC biology. Grafting human skin to the nude mouse not only provides a biologic support system for the graft but also is, by design, a system that is devoid of contaminating circulating precursor cell types. Manipulation of the experimental conditions is quite easy and provides a highly specific means to investigate many parameters of LC function.

Association between plaque accumulation and Langerhans cell numbers in the oral epithelium of attached gingiva

After gingival health had been achieved in four subjects they were instructed to cease all oral hygiene measures. At 0, 8 and 21 days Plaque and Gingival Indices were recorded and gingival biopsies were removed from the buccal aspect of a first molar. Frozen sections of the gingival oral epithelium were stained for ATPase and 5'-nucleotidase to determine the number of Langerhans cells in a defined cross-sectional area. It was found that, as plaque accumulated, there was a statistically significant increase in the number of Langerhans cells in oral epithelium, particularly in the stratum spinosum. These results indicate that dental plaque can elicit a response in Langerhans cells located in the oral epithelium of the gingiva.

Expression of HLA-DR antigen in skin from patients with psoriasis

Using murine monoclonal antibodies against human HLA-DR antigen and against human T cells, we investigated the indirect immunofluorescence staining pattern of involved and uninvolved skin from patients with psoriasis. The staining pattern of involved psoriatic epidermis is different from the pattern seen in uninvolved skin from the same patient and consists of scattered, single HLA-DR positive cells alternating with groups of HLA-DR positive cells. These HLA-DR positive cell clusters can be seen at any level of the epidermis. In some patients, the dermis of involved skin shows prominent accumulations of T cells which are HLA-DR positive and thus represent activated T cells.

The Langerhans cell: the master key to contact dermatitis: a hypothesis

A tentative model is presented which is based on existing published data. The model suggests that the epidermal Langerhans cell plays a central role in contact dermatitis by proliferation control of keratinocytes and as the most peripheral outpost of the immune system. Contact dermatitis to chemicals is the injurious expression of a defense mechanism designed phylogenetically against arthropods and insects.

Effect of oral methoxsalen photochemotherapy on human Langerhans cell number. Dose-response and time-sequence studies

In human adult volunteers, oral 8-methoxypsoralen and UVA (PUVA) caused an almost linear dose-response effect in depleting adenosine 1--5 J/cm2 were used. A higher dose did not appreciably augment the LC depleting effect although the intensity of the PUVA-induced skin inflammation increased. After a single PUVA dose of 5 J/cm2, a nadir in LC density was achieved on day 8 after irradiation, with a decrease from the starting mean count of 704 +/- 58 cells/mm2 to 195 +/- 173 cells/mm2. On day 15 after irradiation, the LC count was still low (261 +/- 249 cells/mm2). In comparison, a single erythematogenic irradiation with a medium-pressure mercury lamp emitting mainly UVB caused an LC depletion which was less intensive, peaked earlier and was almost completely restored by day 15. With both modalities morphological changes were induced in the LC, manifested initially as a shortening of the dendritic processes and later as cell enlargement and dendrite elongation.

Langerhans cells in dermoid cysts: transmission electron microscopic, cytochemical and immunofluorescent observations

Langerhans cells were detected in squamous, stratified epithelia lining human dermoid cysts. Their presence was assayed by ATPase staining and reactivity with heteroantisera against "Ia-like" antigens. Transmission electron microscopic studies demonstrated variations in the numbers of cells showing Birbeck granules in epithelia with different degrees of keratinization. Indeterminate cells (i.e. lacking granules), were more frequent in epithelia showing combined mucous and keratinizing differentiation. Membrane-coating-granules and keratohyalin granules were present in epithelia containing Langerhans cells with clearly identifiable Birbeck granules. Interepithelial mast cells were observed in epithelia with mucous differentiation. A relationship between Langerhans cells and keratinization was suggested. Such non-immune functions are compatible with the known macrophage characteristics of the cell.