Langerhans cells as macrophages in skin and lymphoid organs

Anandamide modulation of monocyte-derived Langerhans cells: implications for immune homeostasis and skin inflammation

Introduction

The endocannabinoid system (ECS), named after the chemical compounds found in the cannabis plant, is a regulatory network of neurotransmitters, receptors, and enzymes that plays crucial roles in skin health and disease. Endogenous ligands of the ECS, called endocannabinoids, have proven to be important regulators of immune responses. One of the most prevalent endocannabinoids, arachidonoylethanolamide (also known as anandamide), is known for its anti-inflammatory effects. Langerhans cells (LCs) are the sole antigen-presenting cells present in the human epidermis. They serve as the first line of defense against pathogens and are essential for the skin's specific immune responses and play a critical role in maintaining tissue homeostasis; however, little is known about the effect of endocannabinoids on these cells. Our research aimed to provide the connection between monocyte-derived Langerhans cells (moLCs) and the ECS, shedding light on their collaborative roles in immune homeostasis and inflammation.

Methods

Human monocytes were differentiated into moLCs using established protocols. Anandamide was applied during the differentiation process to test its effect on the viability, marker expression, and cytokine production of the cells, as well as in short term treatments for intracellular calcium measurement. TLR ligands applied after the differentiation protocol were used to activate moLCs. The impact of anandamide on the functionality of moLCs was further assessed using differential gene expression analysis of bulk RNA-Seq data, moLC-T cell cocultures, while ELISpot was employed to determine polarization of T cells activated in the aforementioned cocultures.

Results

Anandamide did not significantly affect the viability of moLCs up to 10 µM. When applied during the differentiation process it had only a negligible effect on CD207 expression, the prototypic marker of LCs; however, there was an observed reduction in CD1a expression by moLCs. Anandamide had no significant effects on the maturation status of moLCs, nor did it affect the maturation induced by TLR3 and TLR7/8 agonists. MoLCs differentiated in the presence of anandamide did however show decreased production of CXCL8, IL-6, IL-10 and IL-12 cytokines induced by TLR3 and TLR7/8 activation. Anandamide-treated moLCs showed an increased capability to activate naïve T cells; however, not to the level seen with combined TLR agonism. RNA sequencing analysis of moLCs differentiated with anandamide showed modest changes compared to control cells but did reveal an inhibitory effect on oxidative phosphorylation specifically in activated moLCs. Anandamide also promoted the polarization of naïve T cells towards a Th1 phenotype.

Discussion

Our results show that anandamide has nuanced effects on the differentiation, maturation, cytokine secretion, metabolism and function of activated moLCs. Among these changes the decrease in CD1a expression on moLCs holds promise to selectively dampen inflammation induced by CD1a restricted T cells, which have been implicated as drivers of inflammation in common inflammatory skin conditions such as psoriasis, atopic dermatitis and contact dermatitis.

A comprehensive exploration of diverse skin cell types in the limb of the desert tortoise (Testudo graeca) through light, transmission, scanning electron microscopy, and immunofluorescence techniques

The Greek tortoise, inhabiting harsh desert environments, provides a compelling case for investigating skin adaptations to extreme conditions. We have utilized light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and immunofluorescence analysis to describe the structure of the arid-adapted limb skin in the Greek tortoise. Our aim was to identify the cell types that reflect the skin adaptation of this tortoise to arid conditions. Utilizing seven antibodies, we localized and elucidated the functions of various skin cells, shedding light on how the tortoise adapts to adverse environmental conditions. Our findings unveiled numerous scales on the limbs, varying in size and color, acting as protective armor against abrasions, bites, and other potential threats in their rocky habitats. The epidermis comprises four layers: stratum basalis, stratum spinosum, peri-corneous layer, and stratum corneum. Cytokeratin 14 (CK14) was explicitly detected in the basal layer of the epidermis, suggesting a role in maintaining epidermal integrity and cellular function. Langerhans cells were observed between epidermal cells filled with ribosomes and Birbeck granules. Numerous dendritic-shaped Langerhans cells revealed through E-Cadherin signify strong immunity in tortoises' skin. Melanophores were identified using the Melan-A antibody, labeling the cytoplasm, and the SOX10 antibody, labeling the nucleus, providing comprehensive insights into melanophores morphology and distribution. Two types of melanophores were found: dendritic below the stratum basalis of the epidermis and clustered oval melanophores in the deep dermal layer. Varied melanophores distribution resulted in a spotted skin pattern, potentially offering adaptive camouflage and protection against environmental challenges. Numerous myofibroblasts were discerned through alpha-smooth actin (α-SMA) expression, indicating that the Greek tortoise's skin possesses a robust tissue repair and remodeling capacity. B-cell lymphocytes detected via CD20 immunostaining exhibited sporadic distribution in the dermis, concentrating in lymphoid aggregates and around vessels, implying potential roles in local immune responses and inflammation modulation. Employing Tom20 to identify skin cells with abundant mitochondria revealed a notable presence in melanophores and the basal layer of the epidermis, suggesting high metabolic activity in these cell types and potentially influencing cellular functions. These findings contribute to our comprehension of tortoise skin anatomy and physiology, offering insights into the remarkable adaptations of this species finely tuned to their specific environmental habitats.

Peripheral vascular disease: preclinical models and emerging therapeutic targeting of the vascular endothelial growth factor ligand-receptor system

Introduction: Vascular endothelial growth factor (VEGF)-A is a sought therapeutic target for PAD treatment because of its potent role in angiogenesis. However, no therapeutic benefit was achieved in VEGF-A clinical trials, suggesting that our understanding of VEGF-A biology and ischemic angiogenic processes needs development. Alternate splicing in VEGF-A produces pro- and anti-angiogenic VEGF-A isoforms; the only difference being a 6-amino acid switch in the C-terminus of the final 8th exon of the gene. This finding has changed our understanding of VEGF-A biology and may explain the lack of benefit in VEGF-A clinical trials. It presents new therapeutic opportunities for peripheral arterial disease (PAD) treatment.Areas covered: Literature search was conducted to include: 1) predicted mechanism by which the anti-angiogenic VEGF-A isoform would inhibit angiogenesis, 2) unexpected mechanism of action, and 3) how this mechanism revealed novel signaling pathways that may enhance future therapeutics in PAD.Expert opinion: Inhibiting a specific anti-angiogenic VEGF-A isoform in ischemic muscle promotes perfusion recovery in preclinical PAD. Additional efforts focused on the production of these isoforms, and the pathways altered by modulating different VEGF receptor-ligand interactions, and how this new data may allow bedside progress offers new approaches to PAD are discussed.I.

Progress in Tumor-Associated Macrophages: From Bench to Bedside

Tumor-associated macrophages (TAMs) are of great interest in cancer immunology as they play an important role in the tumor microenvironment as cancer stromal cells recruited from circulating monocytes. TAMs are closely associated with tumor progression, including initiation, trophic growth, metabolism, angiogenesis, and metastasis; moreover, in clinical practice, their quantity can be related to poor prognosis. Fundamental and translational studies imply that TAMs are one of the most promising targets in tumor therapy. Herein, the biological origination and classification of TAMs, which correspond to their functions and differentiations, are reviewed in detail. In addition, recent basic research and clinical preprocess of TAMs in tumor immunotherapy are also discussed. Finally, the advances in the use of nanotechnology and TAMs for tumor therapy are discussed. This review focuses on the background and status of basic research and clinical significance of TAMs, points out the potential of TAMs in tumor immunological therapy, and clarifies the possibility of translation TAM-targeting therapies in medicine.

Radiovaccination Hypothesis

The details of patients who have entered remission from metastatic melanoma following palliative radiotherapy are reported. We review the relevant immune physiology and radiotherapy particulars and propose the hypothesis that radiovaccination with high fractional dose to skin metastases can stimulate the development of a robust systemic anti-tumoral immune response capable of causing remission of metastatic disease.

Dendritic Cells in the Immune System—History, Lineages, Tissues, Tolerance, and Immunity

The aim of this review is to provide a coherent framework for understanding dendritic cells (DCs). It has seven sections. The introduction provides an overview of the immune system and essential concepts, particularly for the nonspecialist reader. Next, the “History” section outlines the early evolution of ideas about DCs and highlights some sources of confusion that still exist today. The “Lineages” section then focuses on five different populations of DCs: two subsets of “classical” DCs, plasmacytoid DCs, monocyte-derived DCs, and Langerhans cells. It highlights some cellular and molecular specializations of each, and also notes other DC subsets that have been proposed. The following “Tissues” section discusses the distribution and behavior of different DC subsets within nonlymphoid and secondary lymphoid tissues that are connected by DC migration pathways between them. In the “Tolerance” section, the role of DCs in central and peripheral tolerance is considered, including their ability to drive the differentiation of different populations of regulatory T cells. In contrast, the “Immunity” section considers the roles of DCs in sensing of infection and tissue damage, the initiation of primary responses, the T-cell effector phase, and the induction of immunological memory. The concluding section provides some speculative ideas about the evolution of DCs. It also revisits earlier concepts of generation of diversity and clonal selection in terms of DCs driving the evolution of T-cell responses. Throughout, this review highlights certain areas of uncertainty and suggests some avenues for future investigation.

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

HYPOTHESIS

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Cyclooxygenases and prostaglandins: shaping up the immune response

The relevance of cyclooxygenases (COX)-1 and -2 and their products to inflammation, thrombosis and gastroprotection are well known. Their importance in the immune response was first recognized more than 25 years ago, but has only gained widespread attention recently. In this review, we attempt to integrate information on prostanoids and both the innate and acquired immune responses, including effects on leukocytes, antigen presenting cells, dendritic cells, T and B lymphocytes. Prostanoids may be relevant to immunotolerance, autoimmune disorders, transplantation, immunologic defense against tumors, acquired immunodeficiencies and viral infections. Insight into the role of prostanoids in immune function may afford novel therapeutic opportunities.

Dermal dendrocytes participate in the cellular pathology of experimental acute graft-versus-host disease

In a well established murine model relevant to human disease, graft-versus-host disease results from recognition of recipient minor histocompatibility antigens by donor bone marrow-derived T lymphocytes. Previous studies suggest that factor XIIIa-positive dermal dendrocytes may be involved in the pathogenesis of disorders involving antigen presentation to T cells and dermal fibrosis. This study was undertaken to determine (i) whether normal murine skin contains factor XIIIa-positive dermal dendrocytes, and (ii) whether such cells participate in the pathophysiology of acute graft-versus-host disease. Graft-versus-host disease was produced using B10.BR CD8+ donor T cells administered to CBA recipients. Skin samples were collected weekly for a 5-week period and evaluated by immunohistochemistry and electron microscopy. Our data indicate that normal murine dermis contains factor XIIIa-positive cells localized primarily around deep dermal microvessels. Ultrastructural analyses reveal these cells to have long processes, pinocytotic vesicles, fibronexuses, and intimate associations with mast cells. During graft-versus-host disease, factor XIIIa-positive dendrocytes appeared within the superficial dermis. By ultrastructure, the dendrocytes were hypertrophic and highly branched, and demonstrated an intimate relationship with neighboring cells. In conclusion, factor XIIIa-positive dendrocytes comprise a normal component of the murine dermis and undergo alterations in experimental acute graft-versus-host disease consistent with participation in disease pathophysiology.

Distribution of Langerhans cells in human hair follicle

Using immunohistochemical techniques, we mapped and quantified the distribution of Langerhans cells (LCs) within the follicular epithelium of normal human skin in serial horizontal sections. Ten skin biopsies from disparate, disease-free sites from individuals of various skin types were stained with antibody to CD1a. LCs concentrated in the infundibular epithelium (x=16.16 cells), including the follicular bulge, and extended into the germinative sebaceous epithelium (x=8.84). In contrast, rare LCs (x=1.06) were observed in the follicular epithelium below the entry of sebaceous glands into the follicle. LCs were absent in bulbar epithelium. This infundibulocentric distribution of LCs corresponds to the pattern of follicular inflammation in the scarring folliculitides of lupus erythematosus and lichen planopilaris, as well as allogeneic graft versus host reaction and infundibulofolliculitis of atopy. Follicular LCs may act as the trigger and/or target for these T cell-mediated inflammatory processes.

New insights into tumor-host interactions in lymphoma metastasis

The metastatic process is characterized by a complex series of sequential steps involving constant interactions (mutual "cross-talks") of metastasized tumor cells with their microenvironment (lymphocyte, macrophages, endothelial cells, etc.) in target organs. These interactions determine the outcome of metastasis (either the eradication of metastatic cells or their increased proliferation and invasion). Recently developed methods of tumor and host cell analysis at the molecular level allow better elucidation of molecular mechanisms of metastasis and of immune mechanisms involved in antitumor responses. Direct modulation of these processes will probably increase the success of clinical cancer treatment. Here we review data (a) on the expression of some costimulatory (MHC class II, CD80, sialoadhesin) and adhesion (LFA-1, ICAM-1, VLA-4) molecules on both metastasized tumor cells and host cells and (b) on the production of a cytotoxic molecule, nitric oxide, by in situ activated Kupffer and endothelial cells in the process of liver metastasis. This study was performed with well-characterized murine ESbL T lymphoma cells transduced with the bacterial lacZ gene, which allows detection and quantification of metastases at the single cell level throughout lymphoma growth and metastasis. Experimental results are discussed in the context of recent literature.

Differentiation of Langerhans cells from interdigitating cells using CD1a and S-100 protein antibodies

The present study shows that Langerhans cells can be differentiated from interdigitating cells at the light microscopic level. Superficial lymph nodes and skin taken from necropsies and the lymph nodes of dermatopathic lymphadenopathy (DPL) were used for this experiment. Sections of lymph node and skin were embedded using the acetone, methyl benzoate and xylene (AMeX) method and dendritic cells were immunostained with anti S-100 protein antibody (S-100, and OKT-6 (CD1a) using the restaining method. Langerhans cells in the skin were positive for both CD1a and S-100. Dendritic cells positive for both CD1a and S-100, and dendritic cells positive for S-100, but not for CD1a were observed in superficial lymph nodes. In normal superficial lymph nodes, there were more interdigitating cells than Langerhans cells. The majority of the dendritic cells in the DPL were Langerhans cells. We conclude that the S-100 and CD1a positive cells are Langerhans cells, and the S-100 positive-CD1a negative cells are interdigitating cells.

Susceptibility and resistance to cyclosporin A-induced autoimmunity in rats

Lethally irradiated Lewis (LEW) rats, reconstituted with syngeneic bone marrow and next given Cyclosporin A (CyA) for several weeks, develop disease (Cyclosporin A-induced autoimmunity; CyA-AI) after withdrawal of CyA. This disease resembles in terms of dermal changes the acute dermatitis and chronic scleroderma also seen in graft-versus-host disease (GVHD). In this study we report the relative resistance of the Brown Norway (BN) rat strain to the induction of CyA-AI. In contrast to LEW rats, in which CyA-AI was originally described, BN rats showed no acute dermatitis or scleroderma-like skin pathology in spite of comparable changes in the thymus and a maturation arrest of CD4+ T cells. The difference was also demonstrated functionally for whereas in LEW rats delayed-type hypersensitivity (DTH) reactions could not be elicited during CyA-AI, these were within normal limits in BN rats subjected to the same protocol; NK activity on the other hand was unaffected in both strains. The observation that BN rats developed very mild late disease as evidenced by a slight though significant weight loss suggests that the BN strain is susceptible to the disease but that lesser effector cell generation or, alternatively, stronger suppressor cell responses may prevent dermal disease. These observations may contribute to the elucidation of the mechanisms involved in this experimental autoimmune disease.

Inhibition of Langerhans cell ATPase and contact sensitization by lanthanides--role of T-suppressor cells

Lanthanides are rare earths, elements 55-71 in the periodic table, that are of interest in biologic systems as isomorphic competitors for calcium binding sites. Lanthanides were tested for their inhibitory influence on the Ca++/Mg(++)-dependent ATPase of epidermal langerhans cells in vitro, and on the immunologic function of Langerhans cells in vivo. The trivalent ions of lanthanides, lanthanum, and cerium completely inhibited the ATPase staining of Langerhans cells in vitro. When mice were sensitized with dinitrofluorobenzene on skin sites pretreated with topical lanthanum chloride, and challenged on untreated ear skin, a markedly reduced contact hypersensitivity response was observed. This hyporesponsiveness was found to be antigen specific, and could be passively transferred to naive syngeneic animals recipients by CD4-CD8+ spleen cells. These results suggest that inhibition of the epidermal Langerhans cell surface ATPase by application of topical lanthanum and the induction of antigen-specific immunologic tolerance may be related events.

Prognostic significance of accessory cells and lymphocytes in nasopharyngeal carcinoma

Forty-five consecutive biopsy specimens of nasopharyngeal carcinoma (NPC) and 10 biopsies of healthy nasopharyngeal mucosa obtained from non-cancer patients were investigated by immunohistochemical methods. Monoclonal (B2, T1) and policlonal antibodies (against S-100 protein and lysozyme) with reference to infiltrating lymphocytes and accessory cells (monocytic/macrophagic and dendritic cells) were used. Variable population densities of dendritic cells (S100+) were demonstrated in 22 out of the 45 cases (49%) of NPC; the distribution of these cells was typically within the cancer nests. Monocytic/macrophagic cells (Lys+) were found along the tumor margins and interspersed among the tumor cells in 14 out of 45 (31%) cases. No significant statistical correlation between density of accessory cells and histological type of NPC (classified according to Micheau criteria) was found. Cases with a moderate to marked density of dendritic and monocytic/macrophagic cells survived longer than those with a slight one (mean survival of 63%, 67% and 29%, 27% respectively). In NPC tissues T-lymphocyte infiltration was prevalent. In contrast, B cells were numerous and T cells rare in normal control tissues. The intensity of T-cell infiltration was significantly high in cases with a marked density of S-100+ cells, according to the ability of these cells to present antigens to sensitized T-cells. This study suggests a prognostic significance for reactive cells infiltrating NPC, which means longer survival for cases associated with marked infiltration density of accessory cells.

Interdigitating Reticulum Cell Sarcoma Positive immunohistochemistry for HLA-DR and two other activation antigens, CD30(Ki-1) and CD25(IL2R)

This communication reports a case of the rare interdigitating reticulum cell (IDRC) sarcoma of lymph nodes in a 46-year-old man. Extensive immunophenotypic analysis on paraffin and frozen sections revealed positivity on the neoplastic cells for protein S-100 as well as for antigens CD1, HLA-DR, CD4, CD25 (IL2R) and CD30 (Ki-1). The simultaneous positivity for the three activation antigens CD30, HLA-DR, and IL2R, a phenomenon mostly described in H and S-R cells of Hodgkin's disease, is discussed in particular.

Epidermal cell surface-associated IgG in patients with primary Sjögren's syndrome: in vitro evidence for immune complex binding

In vivo deposits of IgG have previously been demonstrated in the epidermal intercellular area of clinically unaffected skin from 68% of patients with primary Sjögren's syndrome (primary SS). This study compared circulating IgG from patients with primary SS with that from secondary SS in their ability to bind normal human epidermal cells in vitro. We observed a granular pattern of IgG binding to the normal epidermal cell surfaces with 9 of 18 sera from patients with primary SS (50%), 3 of 19 sera from patients with SS secondary to rheumatoid arthritis (16%) (p = 0.025), and none of 24 normal control sera (p less than 0.001). In a subsequent analysis of polyethylene glycol separated sera from two normal controls and two primary SS patients, the epidermal IgG binding capacity was found only in the precipitates of the patients. These findings support our previous hypothesis that the in vivo intraepithelial IgG deposits in primary SS patients are due, at least in part, to cell surface-bound immune complexes.

Mechanisms of dendritic cell function

There is now considerable evidence, from in vivo and in vitro studies, supporting the claim that dendritic cells are the principal accessory cells of the vertebrate immune system. Until recently, however, the biology of the dendritic cell accessory mechanism has remained obscure. Here, Philip King and David Katz review recent findings that have clarified several aspects of this mechanism, providing a possible basis for the potent T-cell stimulating capacity of the dendritic cell, and yielding clues to the ontogenetic relationships of these cells and to their role in immunopathology.

Adhesion molecules on the plasma membrane of epidermal cells. II. The intercellular adhesion molecule-1 is constitutively present on the cell surface of human resting Langerhans cells

The intercellular adhesion molecule-1 (ICAM-1), which is a member of the immunoglobulin superfamily, is expressed on many cell types, including a variety of cells showing accessory/antigen-presenting capacities and belonging to the monocyte/macrophage or dendritic lineages. Here it is shown that human freshly isolated Langerhans cells (LC) constitutively express ICAM-1, as expected. It seems likely that the amounts of ICAM-1 moieties expressed on the plasma membrane of resting LC are only limited, since they virtually escaped detection by conventional immunofluorescence procedures on epidermal sheets. However, all the observed Birbeck granule-bearing LC showed their clear, although relatively weak, ICAM-1 positivity when more sensitive techniques were employed, such as colloidal gold-immunoelectronmicroscopy using gold particles 15nm in size and, to an even higher extent, using gold particles 5 nm in size. Because ICAM-1 is a ligand for the adhesive molecule LFA-1, which is expressed on the surface of leukocytes and, especially, lymphocytes, the ICAM-1 (LC)/LFA-1 (T-lymphocytes) interactions might, enabling these cells to adhere together, deliver activation signals to T cells, thus constituting the initial event in the generation of a cutaneous immune response.

Accessory cells in normal human and rodent lymph nodes: morphology, phenotype, and functional implications

This chapter provides a brief review of the professional accessory cells present in normal human and rodent lymph nodes. When dealing with the function of accessory cells in the immune system it has to be borne in mind that in principle all cells may possess or acquire the capability of antigen presentation, which is the decisive initiating step in the specific host defense bound to the lymphoid cells. Professional accessory cells are arrayed at the afferent limb of the immune response. The majority of them have a typical dendritic morphology, so that the term "dendritic cells" is widely used instead of the term "accessory cells," and has replaced the traditional terms "reticulum cells" and "reticular cells." Professional accessory cells are characterized by: 1. The capability to stimulate specific T- or B-cell response following antigen pulsing 2. A dendritic morphology 3. Expression of major histocompatibility glycoproteins, complement, and Fc receptors as well as of various adhesion molecules. 4. Presentation of processed or unprocessed native antigens 5. Production and secretion of interleukin-1 and interleukin-6 The bimodal differentiation of lymphocytes seems to be reflected in the occurrence of two types of dendritic accessory cell: accessory cells involved in cellular (T accessory cells) and humoral (B accessory cells) immunity. T accessory cells of the lymph node comprise: 1. The lymphoid dendritic cell of Steinman, which probably represent a subset of blood monocytes with possible terminal differentiation into other T accessory cells 2. Veiled cells, which have been shown to represent Langerhans cells of the epidermal covering on their way to thymus-dependent areas of lymph node, probably giving rise to interdigitating dendritic (reticulum) cells 3. Interdigitating dendritic (reticulum) cells as the typical accessory cells of lymphoid T zone The T accessory cells share morphological, ultrastructural, immunophenotypic, and functional properties, are myeloid in origin, and very probably derive from monocyte lineage. As immune stimulatory cells they present processed antigen only and initiate T-cell proliferation and differentiation by interleukin-1 and -6 secretion. Accessory cells involved in the initiation of a primary humoral immune reaction have not been convincingly characterized. Accessory cells responsible for a secondary B-cell response, however, are the so-called follicular dendritic (reticulum) cells constituting the typical web-like structure of the primary and secondary lymphoid follicles. Unlike T accessory cells, follicular dendritic (reticulum) cells are distinguished by accentuated membrane desmosomes and extensive anastomosing branches of dendrites.(ABSTRACT TRUNCATED AT 400 WORDS)

An immunohistochemical and immunoelectron microscopic study of the ontogeny of rat Langerhans cell lineage with anti-macrophage and anti-Ia monoclonal antibodies

An immunohistochemical study with anti-macrophage and anti-Ia monoclonal antibodies was performed to clarify the relationship between Langerhans cells (LC) and indeterminate cells (IC) in rat epidermis both in adulthood and in the fetal stage. On immunoelectron microscopy, a mouse anti-rat macrophage monoclonal antibody, TRPM-1, recently produced by us, reacted with IC and some LC in adult rat skin. Ontogenic study revealed that TRPM-1-positive cells first appeared in the epidermis of fetal rat heads on Day 17 of gestation and then spread caudally along the anterior-posterior axis. On Day 20 of gestation, when the distribution of the TRPM-1-positive cells over body surface became even, Ia-positive cells appeared in the epidermis and began to increase in number. Ia-positive cells with Birbeck granules were found on Day 21 of gestation. These results indicate that. TRPM-1-positive IC matured into Ia-expressing LC after being exposed to microenvironmental change during the perinatal period. The number of Ia-positive cells exceeded that of TRPM-1-positive cells at around 5 d after birth. Afterwards, there were more dendritic Ia-positive cells found in the interfollicular areas than TRPM-1-positive ones. However, local concentrations of the TRPM-1-positive IC in the follicular infundibula were frequently found in the fetal stage and occasionally in adulthood. These TRPM-1-positive cells in the follicular infundibula were thought to be a precursor pool in the epidermis for LC.

Langerhans cells in oral epithelium of chronically inflamed human gingivae

This study describes the histopathological features and the distribution of oral epithelial Langerhans cells in 19 gingival biopsies originating from an adult Tanzanian population characterized by very poor oral hygiene and severe gingival inflammation. Light-microscopically, all biopsies contained often large inflammatory connective tissue infiltrates, 6 of which predominantly contained plasma cells while the rest were dominated by lymphocytes. Seven specimens contained peculiar accumulations of round lymphoid and dendritic cells in the lower cell layers of the oral epithelium. These phenomena have not previously been demonstrated in human gingiva and deserve further attention in studies on the pathogenesis of periodontal diseases. Immuno-histochemical staining with OKT6, OKT4 and OKT8 antibodies showed markedly increased numbers of OKT6-positive cells in 7 specimens and clusters of OKT4- and OKT8-positive cells in the oral epithelium of 4 specimens. High numbers of OKT6-positive cells were not related to the presence of intra-epithelial, non-keratinocyte infiltrates or large connective tissue infiltrates. The variable numbers of oral epithelial Langerhans cells may therefore result from different bacterial antigens elucidating different responses or, alternatively, reflect different responses to similar plaque antigens penetrating the surface of the oral epithelium.

Reduced density and morphologic alteration of Ia and ADPase positive Langerhans cells after low-protein diet

This study examined the effects of low-protein diet on the population density, morphology and histochemical characteristics of Langerhans cells. Weaned at 18 days old, BALB/c mice were divided into two groups: one group received a high-protein diet (20% casein) and the other was fed an isocaloric low-protein diet (caesin 4%). After 14 days, the mice were killed and the skin of the ears was removed for investigation. Langerhans cells were visualized using ADPase and anti-Ia immunoperoxidase techniques. In protein malnourished mice, the density of ADPase and Ia-positive Langerhans cells was significantly reduced, while morphometric assessment of their cross-sectional area showed a significant reduction of total cell area, cell body area and degree of arborization. Quantitative cytophotometric analysis revealed a reduction of ADPase ectoenzyme activity and decreased concentration of membrane Ia antigen. We postulate that these changes affect Langerhans cell functions, and in turn influence the immune mechanisms in the skin.

Immunoregulation of dermatophytosis

Dermatophytoses are superficial infections caused by a group of fungi, the dermatophytes, which invade keratinized tissue of skin, hair, and nails in humans and animals. The importance of normal immune function in resistance to dermatophytoses is substantiated by an increased susceptibility to chronic infection seen in patients with impaired immunological responses. Humoral and cell-mediated immunities are both elicited during the infection. However, specific antibodies to dermatophytes do not seem to play a major role in protective immunity. On the other hand, the development of cell-mediated immunity during the infection is critical in eliciting resistance to the disease. For instance, resolution of the disease in both naturally and experimentally infected humans and animals correlates with the development of delayed-type hypersensitivity (DTH), whereas persistence of infection is frequently accompanied by poor in vitro blastogenic response and absent DTH. Furthermore, in experimentally infected mice, immunity to dermatophyte infection can be achieved by adoptive transfer of lymphoid cells, but not by serum, of infected donors. The present review includes an overview of published work and current research on the cellular events implicated in immunity to dermatophytosis. The role of humoral factors in such immunoregulation is also discussed.

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.

Malignant histiocytosis in childhood: clinical, cytochemical, and immunohistochemical studies of seven cases

Tissue specimens obtained at autopsy from seven childhood cases of malignant histiocytosis were studied by immunohistochemistry. Clinically, the majority of the cases showed sustained fever, hepatosplenomegaly, pancytopenia, and DIC. The pretreatment diagnosis was based on their typical clinical manifestations and bone marrow smear findings. Although three patients temporarily responded to exchange transfusion and chemotherapy, all seven patients eventually died of active disease. Postmortem examination revealed the proliferation of atypical histiocytes appearing in variable degrees of maturation in the lymph nodes, liver, spleen, bone marrow, lungs, and central nervous system. Immunohistochemical staining for lysozyme, nonspecific cross-reacting antigen (NCA), alpha 1-antitrypsin (alpha 1 AT), alpha and beta subunits of S100 protein (S100 alpha, beta), and concanavalin A receptors (ConAR) in cytoplasm demonstrated the presence of two subtypes of malignant histiocytes, ie, S100 beta+/NCA-/ConAR+ (4 cases) and S100 beta-/NCA+/ConA R+ (three cases). The results of lysozyme, alpha 1 AT, and S100 alpha staining were inconsistent. A survey of the literature disclosed that the incidence of S100 protein-positive cases in children was higher than in adults (12/21 v 5/19; chi 2, P less than .05). Further large scale investigation is necessary to confirm the independence and significance of these two subtypes of histiocytes in malignant histiocytosis.

Distribution of Langerhans cells in clinically healthy human gingival epithelium with special emphasis on junctional epithelium

Twenty-one biopsies of clinically healthy marginal gingiva from children, who performed conventional oral hygiene but received no additional professional prophylaxis, were studied in order to obtain information on distribution and density of Langerhans cells (LC) in the oral gingival epithelium (OGE), the sulcular epithelium (SE) and the junctional epithelium (JE). A simple freeze-separation technique was found to create acceptable histomorphology of JE in specimens obtained adherent to teeth, while partially and non-adherent ones were rejected. The majority of LC in OGE were highly dendritic and stained intensively with OKT6 monoclonal antibodies. The distribution was network-like with a density of 21.0 +/- 3.2 LC/0.1 mm2 cross-sectional epithelial area. A similar although less dense distribution was found in SE (8.6 +/- 3.0 LC/0.1 mm2). These observations confirm previous findings. In JE 2 groups of LC were identified: 1) Weakly stained LC with very few and short dendrites distributed in a scattered way (2.8 +/- 1.4 LC/0.1 mm2) in the apical three-fourths of JE in most specimens. Present evidence suggests that these cells might be immature cells of Langerhans lineage. 2) Clusters of LC (9.4 +/- 2.9 LC/0.1 mm2) with dendrites of moderate lengths and numbers and a varied fluorescence intensity; they were found in a few specimens in the coronal one-fourth of JE and at the border zone to SE. Such clusters might represent genuine variation in the distribution of LC or reactions to initial/early plaque formation.

Clinical, ultrastructural immunohistochemical and DNA content analysis of lymphomas having features of interdigitating reticulum cells

Interdigitating reticulum cells (IRC) are dendritic, nonphagocytic histiocytes found in thymus-dependent areas of lymphoid tissues. We report two cases of large cell lymphoma having features of IRC in patients 13 and 17 years old. In each case the diagnosis was suggested by light and electron microscopic features, positive immunoperoxidase staining for S-100 protein, and additional immunoperoxidase findings. Both patients presented with aggressive lymphomas and were treated with intensive combination chemotherapy. Each patient achieved a complete clinical remission, then rapidly relapsed and died with disseminated disease 3 and 9 months after presentation. Novel findings included strong staining of specimens with an antibody to epithelial membrane antigen, staining of one specimen with peanut agglutinin in the pattern previously described in normal IRC, and a DNA content analysis that showed aneuploid stem cell lines in both patients.

Accumulation of Langerhans' cells on the epithelial surface of the lower respiratory tract in normal subjects in association with cigarette smoking

Langerhans' cells are a defined subpopulation of the mononuclear phagocyte system known to accumulate in the lung in histiocytosis X, an interstitial lung disorder strongly linked to cigarette smoking. To evaluate the hypothesis that cigarette smoking itself may be associated with the accumulation of Langerhans' cells in the lung, normal nonsmokers (n = 5) and normal smokers (n = 10) were evaluated by bronchoalveolar lavage for the presence of Langerhans' cells as identified by the OKT6 monoclonal antibody and by transmission electron microscopy. While the OKT6 antibody identified 0.1 +/- 0.1% of the cells recovered from nonsmokers, it labeled 1.1 +/- 0.3% of those recovered from smokers (p less than 0.01). Furthermore, while electron microscopy demonstrated no Langerhans' cells among the lavage cells from nonsmokers, 0.4 +/- 0.1% of the cells recovered from normal smokers contained characteristic intracytoplasmic Birbeck granules, positively identifying them as Langerhans' cells. We conclude that cigarette smoking is associated with an expansion in the population of Langerhans' cells on the epithelial surface of the lower respiratory tract. While the mechanisms underlying this accumulation are unknown, it is possible that the properties of these cells contribute to the derangements of the pulmonary parenchyma found in cigarette smoking and establish a biologic link to the already observed epidemiologic association between histiocytosis X and cigarette smoking.

Quantitative study on phagocytosis of human tonsillar adherent cells by the flow cytometric and immunocytochemical methods

An in vitro phagocytosis assay of adherent cells of 12 palatine tonsils (7 children's and 5 adults' cases with persistent angina) was performed by use of flow cytometry (FCM), using fluorescent latex particles (FLP). The mean value of the percentages of phagocytic cells in the children's group (81.4%) was higher than that in the adults' group (64.0%). In addition, separate immunocytochemical stainings with each antibody--Anti-Leu-M5, OKDR, OKT6, S-100, and lysozyme--were made on smear preparations of a child's and an adult's tonsillar adherent cells after incubation with FLP. By use of the light microscope, the percentages of phagocytic cells in relation to positive cells for each antibody were calculated. The lysozyme positive cell proved to have the highest percentage of phagocytic cells. Then, the average number of phagocytized FLP in one positive cell for each antibody were calculated. With regard to the lysozyme positive cell, this cell proved to have the highest average number of FLP.

Distribution and morphology of macrophages in palatine tonsils

The distribution and morphology of macrophages were studied by immunohistochemical and electronmicroscopic methods in three diseases of the palatine tonsils: tonsillar hypertrophy, recurrent tonsillitis and tonsils with focal infection. We confirmed the presence of two types of macrophages in the tonsils, a monocyte-macrophage cell line and dendritic cells with subtypes, Langerhans' and interdigitating reticulum cells. In the lymphoepithelial symbiosis area and in the subepithelial area, the monocyte-macrophage cells and the dendritic cells had similar distributions and densities. Since these two types of cells were sometimes in contact with each other, they may function in close cooperation. In tonsils with focal infection, there were fewer dendritic cells in the lymphoepithelial symbiosis area, and the germinal centers were less well developed than in the other tonsillar diseases. These findings suggest that in tonsils with focal infection, insufficient amounts of antigen may be presented by the dendritic cells to helper T-lymphocytes.

The regulation of Langerhans cell T6, DR and DQ antigen expression: an hypothesis

A hypothetical model of the maturation pathway of Langerhans cells (LC) within an epithelial environment is presented. This model is based on in vitro studies using human gingival organ culture. In this model, T6 (CD1) antigen is induced on a T6(-) intraepithelial population by Interleukin-1 secreted by epithelial cells. This process is abrogated by a locally produced Interleukin-1 inhibitor, ILS. These T6(+) LC then express first HLA-DR and subsequently HLA-DQ surface antigens under the influence of either lipopolysaccharide or gamma interferon. The induction of these Class II antigens on LC is inhibited by prostaglandin E2. It is postulated that these Class II antigen positive LC are then available to function as antigen presenting cells. This hypothesis is consistent with in vitro studies and several in vivo observations. The basis of the hypothesis is the demonstration that locally produced factors may exert an influence on LC behaviour within an epithelial environment.

Lymph-borne dendritic leucocytes do not recirculate, but enter the lymph node paracortex to become interdigitating cells

Peripheral lymph contains constitutively major histocompatibility complex (MHC) class II-positive, dendritic leucocytes (DL) with a veiled (VC) or dendritic (DC) shape. On the basis of phenotypic similarities to the interdigitating cells (IDC) of T-dependent areas of lymphoid tissues, they are believed, but not yet proven, to be IDC precursors that develop into mature IDC within the draining lymph nodes. In order to determine the relationship between VC/DC and IDC, highly purified radiolabelled peripheral lymph DL (collected by thoracic duct cannulation of mesenteric lymphadenectomized congenitally athymic, nude rats) were reinjected into the veins or footpads of syngeneic recipients. Later, host blood and lymph were collected and the tissues were biopsied and processed for scintillation counting or for light microscopic autoradiography combined with electron microscopy of neighbouring sections. The intravenously injected VC/DC did not enter lymph nodes or Peyer's patches directly from blood and did not re-enter the lamina propria of the gut, but became localized largely in the liver and the spleen. From the liver some of the cells proceeded via afferent lymphatics to the liver and the spleen. From the liver some of the cells proceeded via afferent lymphatics to the coeliac lymph nodes. Similarly, some of the locally injected cells were carried with peripheral lymph to the draining popliteal lymph nodes, although most were retained in the footpads. In the spleen the VC/DC entered the periarteriolar lymphoid sheaths and in the coeliac and popliteal lymph nodes they became localized in the paracortex, where they acquired the morphology of mature IDC.

Langerhans cell histiocytosis: an unusual case illustrating the value of immunohistochemistry in diagnosis

The morphological features of Langerhans cell histiocytosis (histiocytosis X) are characteristic but the diagnosis can on occasion be difficult. A case is presented that illustrates the diagnostic value of immunohistochemistry in the differential diagnosis of this condition. The cells of Langerhans cell histiocytosis were found to express CD1, CD4, CD11b and CD11c. They also reacted with EBM11, UCHM1, KB61 and HLA-DR. Occasional cells showed nuclear staining with Ki67, but no other lymphoid antigens were detected. Immunoreactivity of the cells of Langerhans cell histiocytosis with antibodies that recognize antigens present on macrophages provides further evidence for immunological similarities between these cell types.

Immunohistochemical characterization of intraepidermal in vivo IgG deposits in patients with primary Sjögren's syndrome

68% of patients with primary Sjögren's syndrome have previously been found to have intra-epidermal in vivo IgG deposits in clinically unaffected skin. In this investigation, we examined immunohistologically skin biopsies from 5 patients with primary Sjögren's syndrome and from 5 normal controls in order to characterize further the intra-epidermal IgG deposits. Employing direct immunofluorescence and peroxidase-antiperoxidase (PAP) techniques, IgG was localized to epidermal cell surfaces. Double-labelling immunofluorescence experiments showed IgG to be bound to OKT6-positive Langerhans cells, and to some degree also to keratinocytes. Only IgG1, IgG3 and in one patient IgA were deposited, whereas IgG2, IgG4, IgM, IgD, IgE, C1q, C3c, C3d, C4, beta-2 microglobulin, albumin, fibrinogen and C-reactive protein were not found deposited in the intra-epidermal area. The epidermal IgG deposits were reactive with anti-Fc-fragment antibodies and with staphylococcal protein-A. These results are compatible with, although not definitive proofs of, the hypothesis that the in vivo deposited IgG is found in the form of IgG-containing immune complexes.

Immunohistochemical and ultrastructural studies on histiocytosis in children

Thirty-four cases of eosinophilic granulomas, 18 cases of diffuse histiocytosis-X, 2 cases of Letterer-Siwe-like syndrome with immunodeficiency, 4 cases of malignant histiocytosis and virus associated hemophagocytic syndrome were studied. On paraffin section, S100 protein, lysozyme, alpha-1-anti-trypsin, alpha-1-antichymotrypsin, alpha-2-macroglobulin, Transferrin, Ferritin, peanuts agglutinin, Concanavalin-A, and dolichos biflorus associated antigen were stained by the immunoperoxidase method. In a few fresh materials, T-cell subpopulation by use of monoclonal antibodies (OKT-3, 4, 6, and OK-M1) was examined by the immunoperoxidase method. Two types of Langerhans' cells were found, one is positive for Ferritin and alpha-2-macroglobulin in diffuse histiocytosis-X cells, and another is negative for them in both eosinophilic granulomas. Diffuse histiocytosis-X cell resembled the transformed type of Langerhans cell more than eosinophilic granuloma cells in cellular differentiation. It seemed that the term prolangerhans' cell proliferation disorder might be responsible for it.

Comparative studies of adherent rheumatoid synovial cells in primary culture: characterisation of the dendritic (stellate) cell

Primary cultures of adherent rheumatoid synovial cells contain variable proportions of fibroblasts, macrophages, and dendritic cells, as judged by morphological appearance. Comparative studies using various enzymic and histochemical staining procedures showed the dendritic cells to lack many of the characteristic features of macrophages, e.g. the failure to express HLA-DR (Ia) antigen. The dendritic cells and fibroblasts had several similarities, but differed to some extent in their nonspecific esterase activity, phagocytic and proliferative potential. As the proportions of dendritic cells and fibroblasts varied in relation to specific culture conditions, we examined the possibility that these morphologies might represent different functional states rather than distinct cellular origins. Using subcultured synovial fibroblasts with a uniform bipolar appearance, we have shown that exposure to interleukin-1 or mast cell products resulted in a transformation to dendritic morphology. This change in cell shape was prevented by the presence of indomethacin, but was subsequently achieved by the addition of exogenous PGE2. Thus it appears that the latter is the factor that modulates the morphological change of fibroblastic to dendritic cells. This study has also demonstrated the complete and reversible interchange of fibroblast/dendritic morphology, thereby confirming that these different shapes are manifest by the same cell. The changes in phenotypic expression associated with the dendritic appearance include increased production of collagenase, prostaglandin E, and nonspecific esterase, as well as an apparent inability to exhibit phagocytosis and to proliferate in culture. We conclude from our in vitro studies that the phenotypic behaviour of the synovial fibroblast (or synoviocyte) is very variable and dependent to a large extent upon local stimuli, but the identity and hierarchy of such stimulating and suppressive factors in relation to cellular interactions requires further study.

Extent and diversity of inflammatory cell infiltrates in squamous cell carcinomas and basal cell epitheliomas of the head and neck

Using monoclonal antibodies reactive with Langerhans' cells (LCs), macrophages, and T cell subpopulations, the density and proportions of cells of the immune system of the normal oral mucosa were determined immunohistochemically, and compared with findings in oral squamous cell carcinomas (SCC) and basal cell epitheliomas (BCE). In normal oral epithelia, the dominant cell type was the LC, positive for CD 1, and expressing HLA-DR antigens (DR+). Many intraepithelial cells were lymphocytes of the suppressor/cytotoxic phenotype (CD 8+), which was also the most prominent cell type in the normal mucosal stroma. Significant differences were observed for the content of CD 8-, OKM 1-, and CD 4-positive cells in the epithelium of normal oral mucosa, SCC, and BCE, and for the amount of CD 1-positive Langerhans cells in the connective tissue of the different groups of tissues. When CD 4/CD 8 ratios were calculated, differences between SCC and BCE became most evident. A CD 4/CD 8 ratio greater 0.5 was seen to be characteristic for BCE. Thus, in contrast to the striking preponderance of suppressor/cytotoxic lymphocytes (CD 8+) in SCC, BCE showed typically almost balanced numbers of suppressor/cytotoxic (CD 8+) and helper/inducer (CD 4+) lymphocytes. This finding further underlines the biological differences recognized between these most common neoplasias of the head and neck.

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.

Differential distribution of ATPase- and T6-positive cells (Langerhans cells) in the limbus and cornea of Hereford and non-Hereford cattle

Epithelial sheets from the limbus, cornea, and third eyelid of Hereford and non-Hereford cattle were examined for the presence of Langerhans cells (LC) using the membrane enzyme ATPase as a marker for LC. The aim of the study was to test the hypothesis that differences in LC density exist between the various ocular epithelia of these animals producing depressed immune surveillance in the case of Hereford cattle. The presence of LC in ocular tissues was confirmed by parallel studies which detected epithelial cells bearing T6, an antigen expressed by human LC. Studies using serial sections demonstrated that T6+ cells also reacted with an anti-human HLA-DR monoclonal antibody. The detection of T6+, DR+ and ATPase+ cells in ocular epithelium in the absence of infiltrating macrophages suggested that LC are present in these tissues. While there were no significant differences in the density of T6+ cells between non-Hereford and Hereford cattle, in the latter ATPase+ cells were significantly fewer in the lateral, medial, and upper limbus.

Interleukin-1 modulates T6 expression on a putative intra-epithelial Langerhans cell precursor population

T6 is an antigen which is a highly specific marker for Langerhans cells. Previous studies have demonstrated that Interleukin-1 (IL-1) and an IL-1 inhibitor (ILS) modulate T6 expression (T6E) in explant culture. The present study examined the effects of IL-1 and ILS on T6E in dispersed gingival epithelial cell (EC) cultures. EC were obtained by trypsinization of gingival fragments obtained during periodontal surgery. T6E by EC was demonstrated using OKT6 monoclonal antibody in an immuno-peroxidase technique. In both unseparated and T6-depleted EC, IL-1 (0.5 U/mL) stimulated T6E, and this effect was abrogated by ILS (1:30). ILS alone depressed T6E in unseparated EC cultures. All effects were consistent between four- and 24-hour culture periods, and no treatment affected EC viability, thus excluding cell proliferation or necrosis as a vector for the action of IL-1 and ILS. These results indicate that a population of epithelial cells exists which is induced to express T6 under the influence of IL-1. IL-1 and ILS act in combination to regulate T6E on these precursor cells and on DR(-) Langerhans cells in gingival epithelium.

A monoclonal antibody specifically reactive to human Langerhans cells

We prepared a mouse monoclonal antibody that reacts specifically to human Langerhans cells (LC). The protein recognized by this antibody was mainly in the membranes of Birbeck granules and related structures. Using this antibody, we could identify LC in various tissues; these cells were in the skin, stratified squamous mucosal epithelia, lymph nodes, and the thymus. The antibody did not react with monocytes, tissue macrophages, lymphoid dendritic cells, follicular dendritic cells, or interdigitating cells. The antigen purified with this antibody was a heterogeneously glycosylated protein of Mr approximately 40,000 without interchain disulfide bonds. This antibody may be useful for identifying LC in various human tissues with or without abnormalities, and for studying the origin and fate of Birbeck granules of LC.

Lymphocytic subpopulations in the normal human conjunctiva. A monoclonal antibody study

Monoclonal antibodies were used to analyze the lymphocytic subpopulations in frozen tissue sections of normal human conjunctiva (epibulbar, tarsal, and forniceal). The overwhelming majority of lymphocytes were T-cells (Leu1+ and OKT8+). In the epithelium, the predominant cell type was the OKT8+ cytotoxic/suppressor cell, whereas in the substantia propria, helper T-cells (Leu3a/3b+) equalled suppressor T-cells. T-cells outnumbered B-cells 20-fold; the letter cells were detected only in the substantial propria, particularly in the fornices, and not in the epithelium. Plasma cells, as identified by OKT10 staining, were completely absent except in the accessory lacrimal glands of Krause. Langerhans' cells, identified by OKT6 and HLA-DR (la) staining, were observed in the epithelium of all conjunctival regions. Our findings suggest that the reactivity of B-lymphocytes and plasma cells is heavily damped down by T-lymphocytes, thus allying the conjunctiva to other mucosal membranes and the skin as heavily immunoregulated tissues.

A comparison of conjunctival and nonocular dendritic cells utilizing new monoclonal antibodies

Langerhans cells belong to the dendritic cell family. Their presence in the conjunctiva and cornea has been demonstrated by means of various membrane and cytoplasmic markers. Utilizing OKT6, a monoclonal antibody that specifically binds to Langerhans cells in conjunction with la histocompatibility antigens (HLA-DR), and a new panel of monoclonal antibodies, we compared the population density and characteristic phenotypes of Langerhans cells in normal conjunctiva with those in normal epidermis. A greater density of Langerhans cells was noted in epidermis in comparison with conjunctiva. Various areas of the conjunctiva and cornea were mapped for Langerhans cell distribution. The T6/la ratio of Langerhans cells in conjunctiva was notably different from that in skin. Utilizing the Prolm2 marker, we identified non-Langerhans dendritic cells in the substantia propria and in the basilar epithelium of the conjunctiva, antigen-processing cells probably identical to the interdigitating dendritic cells of lymph nodes.

A new method for intraoral patch testing

Intraoral patch testing was performed in 3 subjects, 2 of whom were contact sensitive to nickel. Maxillary acrylic plates carrying test pieces containing 66% nickel were applied for 48 h, and readings were performed 24 h after removal. Few if any clinical signs were detected, but biopsies from the mucosal contact sites showed lichenoid reactions. Biopsies from control sites showed no or slight non-specific inflammatory reactions.

Modulation of class II (DR and DQ) antigen expression on gingival Langerhans cells in vitro by gamma interferon and prostaglandin E2

The effect of human and murine gamma interferon (IFN-gamma) on Class II (DR and DQ) expression by human gingival Langerhans cells (LC) was examined using an organ culture system. Human and murine IFN-gamma increased the expression of both DR and DQ antigens during a 72-h period. Maximal levels of DR expression (100% of T6+ cells) were produced within 6 h of IFN-gamma treatment and were maintained during culture. DQ expression was maximal (100% of T6+ cells) at 18 h and was more labile than DR. The effect of IFN-gamma on DR and DQ was abrogated by prostaglandin E2 (PGE) while indomethacin, and inhibitor of PGE synthesis, mimicked the effect of IFN-gamma on DR and DQ expression. Gingival keratinocytes maintained their expression of DR for 72 h in the presence of gamma-IFN, but did not express DQ under any of the culture conditions used in this study. These results demonstrate that gamma-IFN induces differential expression of Class II antigens in the oral mucosa in vitro, and suggest that gamma-IFN and PGE may be involved in the control of DR and DQ antigen expression in vivo.