Special Review Article

Density of Langerhans Cells in Nonmelanoma Skin Cancers: A Systematic Review

Langerhans cells (LCs) are bone marrow-derived dendritic cells (DCs) that represent 2-3% of the entire cell population of the human skin, known to have an ability to present antigens to T lymphocytes. Moreover, there is evidence that LCs are probably capable of inducing the local cytotoxic type T-cell-mediated response against the tumour-associated antigens. In the past two decades, a dramatic increase has been noted in the incidence of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). The purpose of this study was to critically assess the results of available studies quantitatively assessing the LCs in nonmelanoma skin cancers and try to establish a conclusion of its possible impact on their future treatment. The PubMed, EMBASE, and the Web of Science databases were searched, which returned 948 citations. After a thorough analysis of full article texts, 30 studies have been chosen, including 11 of the BCC, 12 of the SCC specimens, and 7 analysing both tumour types. There was an overall trend towards slightly higher numbers of LCs in BCC than in SCC; however, these tendencies were discrepant between the studies. We presume that such differences could be caused by various staining techniques with a broad spectrum of specificity, including anti-S100, anti-CD1a, and ATPase activity staining used for LCs identification. We hypothesise that as there is a high inconsistency between the results of the studies, as far as the densities of LCs observed in the specimens are concerned, it seems that the mechanism of the influence of LCs on the antitumoural immune response is complicated. Finally, as at present, there is a paucity of available risk scores for the recurrence or progression of BCC or SCC, the creation of classification stratifying that risk including the density of LCs could bring additional information both for the physician and the patient.

Restoring lost gingival pigmentation in the esthetic zone: A case report

BACKGROUND AND OVERVIEW

There is insufficient literature on the lack of oral pigmentation in the esthetic zone. The aim of this case report was to illustrate the potential impact of loss of gingival pigmentation in the esthetic zone, describe its surgical treatment, and discuss the limited literature on this topic.

CASE DESCRIPTION

An African American woman with high smile line had localized loss of gingival melanin pigmentation as a complication after implant failure and attempted guided bone regeneration in site 8. A highly pigmented free gingival graft was collected from the facial-attached gingiva of the maxillary posterior teeth and placed onto the previously de-epithelialized recipient bed in the maxillary front. Some pigmentation of the graft was preserved and was visible a few weeks after surgery; some pigmentation recovered over time. At 6 months after surgery, the patient was satisfied with the esthetics. Complete recovery of pigmentation took 12 months, at which time the patient was ready to proceed with the final prosthetic work.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Gingival pigmentation can be restored using a free gingival graft from a highly pigmented area. When surgical procedures are performed in such cases, loss of gingival pigmentation should be part of the informed consent. However, further research, including histology, is needed.

Ontogeny and homeostasis of Langerhans cells

Langerhans cells (LCs) refer to the dendritic cells (DCs) that populate the epidermis. Strategically located at one of the body's largest interfaces with the external environment, they form the first line of defense against pathogens that breach the skin. Although LCs share several phenotypical and functional features with lymphoid and non-lymphoid organ DCs, they also have unique properties that distinguish them from most DC populations. In this review, we will discuss the key mechanisms that regulate LC homeostasis in quiescent and inflamed skin. We will also discuss recent evidence that suggests that LCs arise from dedicated precursors during early embryonic development.

Antigen-presenting cells, including Langerhans cells, veiled cells and interdigitating cells

The accessory functions attributed to macrophages, such as antigen presentation, are probably carried out by specialized, marrow-derived cells which always have Ia antigen on their surfaces. These cells are not actively phagocytic, but are mainly engaged in engulfing large volumes on fluid. They are found in the epidermis as sessile cells, the Langerhans cells, but some re-enter the dermis and appear in afferent lymph as actively moving, veiled cells. Here they are joined by other veiled cells which have differentiated in the dermis: both populations then enter the draining lymph node. A similar process of differentiation probably occurs in other specialized tissues leading to the formation of cells that enter the afferent lymph and become veiled cells. In the lymph node, veiled cells localize in the paracortex or T-dependent area and later differentiate into another sessile cell type, the interdigitating cell. The life-style of this family of cells appears to be well-adapted for the transport of antigen into the paracortex, an area from which free antigen is largely excluded, and it seems likely that T-cell activation is triggered by the arrival of veiled cells bearing a new antigen on their surfaces.

Langerhans cell histiocytosis research. Past, present, and future

This article reviews the various investigative events that led to the endorsement of the term Langerhans cell histiocytosis for the various clinicopathologic conditions previously called Hand-Schüller-Christian disease, Abt-Letterer-Siwe disease, eosinophilic granuloma of bone, and histiocytosis X. The different denominations reflect the changing conceptual approaches to the so-called reticuloendothelial system and the successive acquisition of new ultrastructural and immunocytochemical data.

Epidermal Langerhans cell development and differentiation

Epidermal Langerhans cells (LC) play a critical role in host defense. Still we know rather little about the development and functional specialization of these bone marrow-derived dendritic cells (DC) located in the most peripheral ectodermal tissue of the mammalian organism. How LC develop from their primitive progenitors in bone marrow and to what extent LC are related in their development to other lineages of the hemopoietic system is still under debate. There are currently 3 major areas of debate: 1) which are the signals required for LC development and differentiation to occur, 2) what are the (molecular) characteristics of the intermediate stages of LC differentiation, and 3) how are LC related in their development and/or function to other cells of the hemopoietic system? A better understanding of LC development and answers to these questions can be expected from recently developed technologies which allow the in vitro generation of DC with the typical molecular, morphological and functional features of LC from purified CD34+ progenitor cells under defined serum-free culture conditions. TGF-beta 1 was found to be an absolute requirement for in vitro LC development under serum-free conditions upon stimulation with the classical DC growth and differentiation factors GM-CSF, TNF-alpha and SCF. The recently identified cytokine FLT3 ligand further dramatically enhanced in vitro LC development and even allowed efficient in vitro generation of LC colonies from serum-free single cell cultures of CD34+ hemopoietic progenitor cells.

E-cadherin is the major mediator of human melanocyte adhesion to keratinocytes in vitro

E- and P-cadherin are calcium (Ca2+)-dependent cell adhesion molecules important in the morphogenesis and maintenance of skin structure. By use of flow cytometry and specific antibodies, we now show that cultured human melanocytes express E- and P-cadherin on their surfaces, and that these molecules have the same characteristics as reported for other cell types. Specifically, melanocyte cadherins are sensitive to trypsin digestion in the absence of Ca2+ and are protected from trypsin degradation by Ca2+, and are functional at 37 degrees C but not at 4 degrees C. We further show that melanocytes contain mRNA transcripts encoding both E- and P-cadherin. Adhesion of cultured melanocytes to keratinocyte monolayers is abolished by pre-treatment of the melanocytes with trypsin/EDTA, which degrades E- and P-cadherins, is greatly reduced by anti-E-cadherin antibodies and is slightly reduced by antibodies to P-cadherin, alpha 2, alpha 3 and beta 1 integrins. In contrast to normal melanocytes, eight of nine melanoma cell lines lacked E-cadherin (or expressed markedly reduced levels) and five were negative for P-cadherin. Melanoma cells also failed to adhere to keratinocyte monolayers. These results demonstrate that normal human melanocytes express functional E- and P-cadherin and that E-cadherin is primarily responsible for adhesion of human melanocytes to keratinocytes in vitro. In addition, transformed melanocytes express markedly reduced levels of E- and P-cadherin, and exhibit decreased affinity for normal keratinocytes in vitro, suggesting that loss of cadherins may play a role in melanoma metastasis.

Growth and differentiation of normal human melanocytes in a TPA-free, cholera toxin-free, low-serum medium and influence of keratinocytes

Melanocyte cultures were obtained from a modification of the keratinocyte culture system MCDB153. Either promelanocytes or mature melanocytes were selected from epidermal cell primary cultures. Pure subcultures of actively dividing melanocytes of both types were grown in a low-serum medium totally deprived of TPA and cholera toxin called melanocyte growth medium (MGM). Early passaged cells from MGM primary cocultures were similar to normal adult human melanocytes in vivo, exhibiting numerous melanosomes, strong dopa positivity and a high dendricity. The ability of MGM to support melanocyte growth was mainly a consequence of its basic composition, combined with a low serum concentration. Bovine pituitary extract significantly enhanced melanocyte growth. Using complete MGM, in the absence of mitogens and keratinocytes, cell growth was maintained, but the differentiation of melanocytes decreased. The presence of keratinocytes was found to promote melanocyte growth. The coculture system used strongly suggests the action of soluble keratinocyte-derived factors. Keratinocyte contact was necessary to sustain melanocyte dendricity and melanization. Melanization and dendricity behaved mostly as independent features when keratinocyte influence was withheld. Our results underline the essential role of keratinocytes in the regulation of melanocyte growth and differentiation in a physiological culture system.

Autologous grafting with noncultured melanocytes: a simplified method for treatment of depigmented lesions

BACKGROUND

Achromic lesions on the trunk and the extremities often do not respond to treatment and little improvement is obtained in cases of segmental vitiligo.

OBJECTIVE

Transplantation of autologous noncultured melanocytes was performed to obtain a successful repigmentation.

METHODS

The grafting method is carried out in two steps: production of blisters on the depigmented lesions by freezing with liquid nitrogen and injection in each blister of a suspension of epidermal cells (mainly keratinocytes and melanocytes). The cellular suspension was obtained from samples of skin of the hair scalp after trypsinization.

RESULTS

Repigmentation was evident within 25 to 30 days. Coalescence of the pigmented areas was spontaneously observed or obtained after UVA stimulation. Patients with two types of leukoderma-vitiligo or nevus depigmentosus had successful repigmentation after transplantation of autologous noncultured melanocytes.

CONCLUSION

This technique appears to be an effective and simple method for treating patients with achromic areas lacking melanocytes.

Keratinocytes regulate melanocyte number in human fetal and neonatal skin equivalents

To determine if keratinocytes influence melanocyte number and position in the developing epidermis we have experimentally recombined keratinocytes and melanocytes from epidermis of different stages of differentiation in the skin equivalent (SE) system. Previously we showed that developmental differences in the position and number of melanocytes characteristic of the epidermis in vivo were preserved in fetal and neonatal skin equivalents. In the present study we have combined cultured fetal or neonatal keratinocytes with age-matched or non-age-matched cultured melanocytes on the dermal equivalent. The ratio of basal keratinocytes to melanocytes (BK/M) present in multiple high-power fields was determined after localization of melanocytes by staining with the melanocyte-specific monoclonal antibody, HMB-45. The BK/M ratio in SE composed of neonatal keratinocytes and either fetal (n = 4) or neonatal (n = 5) melanocytes was 26.2 and 21.5, respectively. The BK/M ratio in SE composed of fetal keratinocytes and either fetal (n = 8) or neonatal (n = 5) melanocytes was 9.2 and 7.7, respectively. In each case, the BK/M ratio was dependent on the keratinocytes rather than the melanocytes. With either type of melanocyte, ratios in SE composed of neonatal keratinocytes were significantly greater than those with fetal keratinocytes. These results establish that keratinocytes regulate the BK/M ratio in this model and suggest that developmental differences between fetal and neonatal keratinocytes may be responsible for determining melanocyte numbers in the epidermal-melanin unit in vivo. The precise mechanisms that control the organization and number of melanocytes in the epidermis are unknown although keratinocytes may interact with melanocytes via growth factors, cell surface molecules, or other factors related to proliferation and differentiation of the epidermis.

Differential expression and activity of melanogenesis-related proteins during induced hair growth in mice

In C57 Bl-6 mice, melanogenesis is strictly coupled to the growth phase of the hair cycle (anagen). To further study this phenomenon of concerted developmental and pigmentary activity, we followed the sequence of tyrosinase (key enzyme of melanogenesis) expression and activity and the presence of the melanosomal protein gp 75 during the development of traumatically induced anagen follicles (days 0 = telogen, and days 1-12, after anagen induction studied). In addition to performing Northern and Western blots for tyrosinase, tyrosine hydroxylase activity (THA) and dopa oxidase activity (DOA) were measured. On day 0, DOA was undetectable, and THA was very low. On days 1 and 2, both activities were undetectable; starting from day 3, they increased rapidly, reaching a plateau on days 8 and 12. DO-positive proteins had apparent molecular weights (MW) of 66-68 kD (days 3-12), 72-74 kD (days 5-12), and 130 kD (days 8 and 12). Western blotting emphasized proteins of MW 66-68 kD (tyrosinase), and 73-75 kD (gp 75); tyrosinase was undetectable on day 0, but already present on days 1 and 2; it increased by day 5 and had reached a plateau on days 8 and 12; gp 75 was undetectable on days 0-2; it was present on day 3, increased by day 5, and reached a plateau on days 8 and 12. Northern blot analysis revealed high levels of tyrosinase mRNA on days 5 and 8, low levels on days 1-3, and none on day 0. These data suggest a highly regulated, time frame-restricted, differential pattern of tyrosinase transcription, translation, and enzyme activity during the different stages of the developing murine anagen follicle, possibly as a result of complex interactions between follicular melanocytes and their environment.

Electron microscopic observations of dyskeratosis, apoptosis, colloid bodies and fibrillar degeneration after skin irritation with dithranol

Dying cells undergo coagulative necrosis or apoptosis. In the skin, apoptosis is known to occur in graft-versus-host reactions, in lichen planus, during regression of plane warts and neoplasms, and after physical injury caused by ultraviolet light resulting in sunburn cells. The present study shows that primary skin irritation also causes apoptosis. Mild, or moderate-to-considerable, dithranol irritation of healthy uninvolved human skin caused focally coagulative necrosis of keratinocytes and also apoptosis of scattered keratinocytes, i.e. condensation of chromatin and cytosol, clumping of tonofilaments and budding of membrane-bound cell fragments. These apoptotic cell fragments were engulfed in the epidermis by macrophages. Colloid bodies were detected in the upper dermis and apparently represented nonphagocytosed apoptotic cell fragments that had dropped down from the epidermis. Dithranol also caused fibrillar degeneration of melanocytes and in some cases of Langerhans' cells, indicating that colloid bodies in the upper dermis could partly derive from these cell types. The significance of apoptosis in irritant contact dermatitis could be to maintain homeostasis of epidermis and counteract the hyperplastic response caused by irritant stimuli. Another possibility is that apoptosis was the response to an injury less severe than that causing necrosis.

Ultrastructural and phenotypic changes in Langerhans cells induced in vitro by contact allergens

Ultrastructural changes of murine Langerhans cells (LC) were examined following exposure of crude epidermal cell suspensions to the contact allergens dinitrochlorobenzene, nickel sulphate and lead nitrate at various concentrations and for various incubation times. An immunogold labelling technique was employed to study changes in surface expression of MHC Class II (Ia) molecules. In all cases, activation of LC was evident after as little as 15 min exposure and was characterized by a marked increase in surface expression of Ia molecules, prominent rough endoplasmic reticulum and numerous ribosomes and lysosomes. Degenerative changes in LC were apparent to varying degrees depending on the allergen, its concentration and the time of incubation. Degenerative changes included swollen mitochondria, membrane disruption or rupture, loss of density of the cytoplasm (cytolysis), loss of dendritic processes and decreased expression of Ia molecules. In the case of dinitrochlorobenzene, degenerative changes were present and usually severe at concentrations greater than 10 micrograms/ml, while exposure to nickel sulphate and lead nitrate was associated with only mild degenerative changes. These observations indicate that contact allergens have a variety of direct effects on LC, including activation and degeneration, which are dose- and time-dependent. Since these alterations of LC were observed in the absence of other immunologically active cells, peripolesis cannot be involved in these events.

Langerhans cells: antigen presenting cells of the epidermis

While epidermis in the skin provides an excellent barrier to the environment, it is an incomplete one. Some antigenic material can penetrate through the stratum corneum (or be introduced pathologically) where strategically placed epidermal Langerhans cells reside. In this review, we have assembled relevant data concerning the antigen presenting potential of epidermal Langerhans cells. Strong circumstantial evidence derived from in vitro studies of epidermal cell suspensions enriched for Langerhans cells indicates that Langerhans cells possess this capability. In vivo studies with intact skin indicate that critical numbers of functioning Langerhans cells are essential for successful induction of contact hypersensitivity by epicutaneously applied haptens. And within the past several months, experiments with purified preparations of epidermal Langerhans cells have proven that these cells, and perhaps they alone among epidermal cells, possess the capacity of processing and presenting haptenic determinants to the immune system. The challenge for the future is to determine the extent to which this unique property of Langerhans cells affords physiologic protection to the skin and under what pathologic circumstances altered Langerhans cell function leads to disease.

Assessment of Langerhans' cells in oral lichen planus using monoclonal antibodies

In order to demonstrate Langerhans' cells in epithelium of oral lichen planus, monoclonal antibodies were used as immunological markers in combination with immunohistochemistry. By the use of anti-Ia antibodies the Langerhans' cells were shown to express an increased number of Ia-like antigens in comparison to the amounts found in healthy oral mucosa. The subepithelial infiltrate of mononuclear cells expressed identical Ia-like antigens on their surfaces. With anti-T6 antibodies as immunological markers, the number of Langerhans' cells was found to be virtually identical in diseased and healthy epithelium. Treatment of oral lichen planus with tretinoin resulted in a decrease of epithelial Ia-like antigens compared with the number found in untreated lesions. However, treatment with tretinoin did not alter the frequency of Langerhans' cell marked with anti-T6 antibodies. The present data demonstrate an increased amount of Ia-like antigens per number of T6-positive Langerhans' cells in diseased oral mucosa compared to healthy conditions. The increased expression of Ia-like antigens on Langerhans' cells and the contemporary finding of Ia-like antigens on the subepithelial T-cells support the opinion that the pathogenesis of oral lichen planus is mainly a cell-mediated type of immunological reaction.

Langerhans cells in squamous exocervical carcinoma: a quantitative and ultrastructural study

The gross morphology, density, distribution, and ultrastructure of the Langerhans cell (LC) in the human exocervix in cases of cervical intraepithelial neoplasia (CIN) and incipient carcinoma were investigated. Two zinc-iodide-osmium (ZIO) procedures were applied to epithelial sheets and to tissue sections for light and electron microscopy. The ZIO methods as well as conventional electron microscopy revealed the presence of LCs in CIN, in the invasive prongs, and in the lymphoid infiltrate of the chorion. The epithelial sheets demonstrated a LC density 3.5 times higher than we have previously reported for the normal exocervix. The region around the external os displayed the highest LC density and the most advanced grades of CIN. The LCs were classified into six types according to the number of processes and secondary branches. The most ramified types were more abundant in the neoplastic exocervix than in the normal exocervix. The LC in all locations of the exocervix with carcinoma showed hypertrophy of the rough and smooth endoplasmic reticula and a large number of filaments. The RER displayed dilated cisternae containing electron-dense material. Specialized contacts between LCs and lymphocytes were an outstanding finding. These findings suggest that the LC might play an important role in the neoplastic process.

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.

Phenotypic expression of epidermal cells in vitro: a review

Disaggregated epidermal cells, sheets of epidermis, and explants of partial and full-thickness skin have been grown in cell, organ, and explant cultures. Each type of epidermal sample has also been "cultured" as a graft on a living animal host. The extent of tissue-specific phenotypic expression by the epidermal cell varies with the type of culture and the culture conditions: medium, biologic and pharmacologic additives, substrate, cell density, pH, and temperature. Specific culture conditions can be chosen to select for certain phenotypic traits. In spite of the diversity of conditions that may be used for culture, keratinocytes in cell, explant, and organ cultures undergo a similar pattern of differentiation. They stratify and keratinize, but rarely express a complete program of keratinization. Many of the characteristics associated with this pattern of differentiation are also observed in fetal epidermis during development. In culture, normal tissue architecture is usually absent; cells organize in flattened, loosely associated layers, synthesize a different pattern of keratin polypeptides, form keratohyalin granules only sporadically, and rarely contain lamellar granules. Epidermal differentiation in explant and organ cultures can be evaluated in regions of the explant, epibolic zone, and outgrowth apron. The epidermis of the original explant undergoes hyperproliferation, degeneration, sloughing, and then regeneration of a thin tissue. The cells in the epithelial outgrowth zone stratify and differentiate almost identically with those in cell culture. Neogenesis of structures in the basement-membrane zone can be followed in all three regions of the explant culture. Sheets of epidermis or epidermal cells transplanted onto or into a host animal show the most complete expression of the epidermal phenotype. After a period of hyperplastic growth, the cell layers become established in a pattern nearly identical to that in vivo. A complete granular layer is formed and stratum corneum cells, which are structurally and biochemically equivalent to those in tissue, differentiate. In some instances, the epidermis reconstructed from cells or tissue is indistinguishable from adjacent host epidermis. Experiments that include serial transfer from one culture system to another demonstrate the plasticity of the epidermal cell and its ability to respond variously to its environment.

Modulation of expression of epidermal Langerhans cell properties following in situ exposure to glucocorticosteroids

Langerhans cells (LC) have been implicated as antigen-presenting and target cells in contact allergic, cell-mediated reactions. We have examined the effects in guinea pigs, rats, and humans of in situ (epicutaneous) exposure to glucocorticosteroids (GCS) on the expression of epidermal LC markers. Reductions in the number of Fc-rosetting, C3b-rosetting, and immune-associated (Ia) antigen-bearing LC occurred in a dose-related fashion, with the degree of such reductions dependent upon the specific GCS employed. These reductions were determined to be reversible following cessation of exposure to GCS. T6 antigenicity, another cell surface marker of human LC, was little affected by GCS exposure. Simultaneous immunofluorescent staining for T6 and Ia antigenicity within human epidermis of amcinonide treated skin detected reduced numbers of T6+/Ia+ cells with a concomitant increase in T6+/Ia- cells. The data presented suggest a selective reduction in the expression of immunologically important receptors and antigens by LC which may be involved in steroid-responsive contact allergic reactions.

Control of melanin synthesis and secretion by B16/C3 melanoma cells

In culture, B16/C3 murine melanoma cells grown in the presence of serum undergo melanogenesis at a specific time after plating. At this time, melanin is synthesized intracellularly and then secreted into the extracellular culture fluid. We have found that melanin secretion is dependent on the presence of serum in the growth medium. When confluent cultures are deprived of serum, that is, refed with serum-free medium, cells remain viable but do not undergo melanogenesis. Addition of serum-free medium supplemented with either melanocyte-stimulating hormone (MSH) or dibutyryl cAMP induced melanogenesis in these cells but did not result in melanin secretion. Furthermore, when B16/C3 cells are grown in serum-free, hormone-supplemented medium, they also undergo melanogenesis but fail to release melanin. The addition of serum, however, to B16/C3 cells induced to undergo melanogenesis with MSH, dibutyryl cAMP, or hormone-supplemented medium promotes melanin secretion. Fractionation studies hence revealed that serum contains specific factors capable of inducing melanin secretion. These results demonstrate that factors that regulate melanin synthesis are distinct from those that induce cells to release melanin into their extracellular environment. Furthermore, the ability to induce melanogenesis with single factors will permit us to study the precise sequence of events leading to differentiation in B16/C3 cells under chemically defined conditions.

Epidermal Langerhans cells in erythrokeratodermia variabilis. Histochemical and ultrastructural investigations before and after treatment with etretinate (RO 10-9359)

The distribution of epidermal Langerhans cells (LC) in erythrokeratodermia variabilis (EKV) was investigated using enzyme-histochemical (ATPase) and immunohistochemical (anti-T6 and anti-HLA-Dr) techniques. Biopsy specimens from lesional skin of five patients were examined before and 8 weeks after treatment with etretinate (RO 10-9359). In addition, electron microscopy studies were carried out in two of these cases. The number of ATPase-positive dendritic cells in lesional epidermis appeared to be remarkably reduced in comparison with normal skin from healthy subjects. After treatment, the number of ATPase-positive dentritic cells had increased but still remained below normal values. Similar but less striking results were found for anti-T6-stained specimens. The HLA-Dr antigen appeared to be unsuitable as a marker for comparative quantitative studies because of the highly variable expression of this antigen in the control specimens. Electron microscopy studies revealed LC in the basal and suprabasal layers of the lesional epidermis. Both before and after treatment, the LC exhibited a normal ultrastructure. In view of the clinical and histologic normalization of the skin lesions during treatment, these findings suggest that the decreased number of epidermal LC may be related to the abnormal keratinization that occurs in EKV.

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.

Studies on human epidermal Langerhans cells III. Induction of T lymphocyte response to nickel sulphate in sensitized individuals

Human epidermis from nickel sensitive patients was separated from dermis by means of a suction blister device and dissociated with trypsin. The epidermal cell suspensions obtained contained 3--5% Langerhans cells as judged by immunofluorescence staining of the cells with a rabbit anti-DR antiserum. The epidermal cells were co-cultured with purified autologous T lymphocytes with or without nickel sulphate. A strong proliferative T lymphocyte response to nickel sulphate was obtained provided epidermal cells were also present. Pretreatment of the epidermal cells with anti-DR antiserum abolished or greatly reduced the response. These data indicate that epidermal cells are able to present nickel sulphate to T lymphocytes in an immunogenic way. Since the responsible cells were DR antigen positive, it is highly probable that the cells responsible for these functions are the Langerhans cells.

Receptors for complement of Langerhans cells

A population of guinea pig epidermal cells, identified as Langerhans cells, formed rosettes with sheep erythrocytes coated with IgM immunoglobulin and C3b (EAC1-3b) but not with intermediates carrying only C1, C14b, or C14b2a. These findings were unusual since most other cells expressing C3b receptors also express C4b receptors. To investigate whether these results were the consequence of a limited number of C4b molecules on the cells, EAC14b cells were prepared with increased amounts of C4b (15 to 250 micrograms on 10(9) cells). EAC14b rosette formation was found with a maximal number when there were 3,000 molecules per cell, a 6-fold excess over that found in previous experiments. One could inhibit this rosette formation by fluid phase C3b as well as by fluid phase C4b, suggesting proximity or possible identity of these 2 receptors.

Expression of Ia antigens on Langerhans cells in mice, guinea pigs, and man

In all mammalian species so far examined, Langerhans cells or their precursors are the only epidermal cells expressing Ia antigens or their equivalents. In man, xenoantisera raised in rabbits against purified B lymphocyte cell membrane antigens were utilized to stain the Langerhans cells, by either fluorescence or immunoferritin methods. A high proportion of the indeterminate cells in the epidermis also expressed HLA-DR antigens, and a relationship to Langerhans cells is suggested. Confirmation of these results was obtained in mouse. Alloantisera raised against I-A and I-EC subregion products again stained only Langerhans cells. Fluorescence, immunoperoxidase, and immunoferritin methods were used, and confirmation of the specificity of the reaction was achieved at the electron microscope level. Langerhans cells were shown, by ATPase staining, to be absent from the epithelium of the central cornea, but were present in the limbus. Population of the entire corneal epithelium surface was induced by application or irritants or contact sensitizing agents such as dinitrochlorobenzene. Grafting of corneas either deficient or populated with Langerhans cells, to skin beds, may answer the question of the influence of such cells on allograft rejection.

Contact hypersensitivity and Langerhans cells

Allergens or antigens when introduced on or in the skin may become localized at the surface of and in Langerhans cells (LCs). Langerhans cells are a strategically situated cell population able to migrate into lymphatics and lymph nodes. During the course of contact allergic reactions, they are apposed to lymphocytes; some LCs are injured by interaction with lymphocytes and by antigen-antibody complexes plus complement. It is not yet clear to what extent these LCs may then release the substances they contain, such as enzymes from lysosomes, and cause further inflammatory changes. In contact dermatitis they appear to play the role of antigen presenters, and may also be target cells and inflammation-producing cells. Since in contact allergy the major antigen presentation occurs via skin, it is likely that the presence of functional LCs with intact Ia antigens is of paramount importance for induction and elicitation of this immune response.

Studies on human epidermal Langerhans cells. I. Allo-activating and antigen-presenting capacity

Human epidermis was separated from dermis by means of a suction blister device and dissociated with trypsin. The epidermal cell suspensions obtained contained 3--5% Langerhans cells as judged by immunofluorescence staining ot the cells with a rabbit anti-DR antiserum. The epidermal cells were co-cultured with purified allogeneic T cells and with autologous T cells with or without PPD of tuberculin. A strong T-cell response to allogeneic epidermal cells was obtained, as was a strong T-cell response to PPD, provided autologous epidermal cells were also present. Pre-treatment of the epidermal cells with anti-DR antiserum plus complement abolished both these responses. These data indicate that epidermal cells are able to substitute for macrophages both in the allo-activating and in the antigen-presenting function. Since the responsible cells were DR-positive, it is highly probable that the cells responsible for these functions are the Langerhans cells.

Langerhans cells and serum precipitating antibodies against fungal antigens in bronchioloalveolar cell carcinoma: possible association with pulmonary eosinophilic granuloma

In an ultrastructural study of 37 cases of bronchioloalveolar cell carcinoma (BAC), we identified seven cases (19%) in which Langerhans cells (LC) were closely associated with tumor cells. Serum precipitating antibodies against Aspergillus species and/or thermophilic actinomyces were present in five BAC patients whose tumors contained LC and in six patients whose tumors lacked LC. In a simultaneous study we identified marked atypical bronchiolar and alveolar lining cell hypertrophy and hyperplasma in pulmonary eosinophilic granuloma (PEG). Our data plus current information suggesting that PEG is a form of hypersensitivity pneumonitis support our hypothesis that those cases of BAC in which LC are present may rise in localized or diffuse pulmonary scars caused by PEG.

Ultrastructure of blebbing phenomenon and phagocytosis of blebs in laryngeal carcinoma

The epithelial-connective tissue junction of invasive squamous cell laryngeal carcinoma was examined electron microscopically. The pleomorphic cytoplasmic protrusions known as blebs were observed on the lateral and basal surfaces of malignant keratinocytes. These blebs were pinched off from the malignant epithelial cells and were then observed in the connective tissue or in the intercellular spaces. After the pinching-off process some blebs were seen to be closely surrounded by pseudopods of phagocytizing histiocytic cells in the lamina propria or by adjacent malignant keratinocytes in the intercellular spaces. Since blebs are believed to be intact parts of viable cells this engulfment can be interpreted as cytophagocytosis. During cytophagocytosis the zeiotic blebs exhibited varying degrees of enzymatic digestion. The process of blebbing was discussed in respect to cellular locomotion of malignant keratinocytes during tumor invasion. This phenomenon seems to occur only in the preliminary stages of malignant tumor growth in the larynx.

Guinea-pig keratinocytes and melanocytes in tissue culture: scanning, transmission and high voltage electron microscope observations

Keratinocytes and melanocytes cultured from guinea-pig epidermis were studied with scanning, transmission and high voltage electron microscopy to characterize the surface and internal morphology. Keratinocytes exhibited contact-inhibition and a range of surface structures consistent with cell-cycle dependent changes. Stereoscopic analysis of high voltage electron micrographs indicated regular oval nuclei with nucleoli at different depths, while thin sections revealed local channels in the nuclei. Secondary cultures differed from primary cultures in the disorder of the microfilaments, in the failure to form desmosomes, and in the failure of melanocytes to persist in culture. The beaded surface of melanocytes was indicative of underlying melanosomes that were seen in high voltage micrographs. Melanocytes were rounded with moderate ruffles or were dendritic with ruffles on the termini. These findings are discussed in relation to the observational techniques and in relation to modes of locomotion of and pigment transfer to epidermal cells.

The ultrastructure of the normal conjunctival epithelium of the guinea pig. I. The basal and intermediate layers of the perilimbal zone

The present paper on the perilimbal zone of the guinea pig conjunctival epithelium describes the ultrastructural organization of the basal cell layer, including basal epithelial cells, melanocytes and small lymphocytes, as well as the intermediate cell layers consisting of polyhedral cells and processes from the melanocytes and the small lymphocytes. Particular attention is paid to those cell features that might be associated with phagocytosis, autophagy, and transport mechanisms.