Langerhans cells: target cells in immune complex reactions

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.

Dendritic cells as targets for cytotoxic T lymphocytes

Dendritic cells (DC) carry antigen into lymph nodes where they may cluster with CD4 and CD8+ lymphocytes and activate both subsets in the initiation of immune responses. Since DC do not leave the lymph nodes in the efferent lymph they may die within the lymph nodes. Another possibility is that they are targets for cytotoxic T cells (CTL) when expressing appropriate epitopes. This possibility was tested in vitro using human peripheral blood DC to stimulate the development of primary CTL in response to HIV-1 or one of its T-cell epitopes (e.g. env 111-126) and secondary CTL in response to type A influenza virus. Pooled CTL generated during six day cultures in 60 replicate 20 microliters hanging drops were tested in a conventional CTL assay. The HIV or HIV peptide stimulated CTL lysed HIV infected DC while the influenza-virus induced CTL killed DC targets infected with this virus. DC were not lysed significantly until they had been exposed to virus for 2-3 days and thus are not highly susceptible to lysis. However, killing of DC after 2-3 days infection with virus may be a feedback mechanism for removing antigen presenting cells after they have stimulated T cell responses. Removal of persistently infected DC by CD8+ CTL may also contribute to the reduction in DC numbers observed in blood and skin in HIV infection.

Three-dimensional reconstruction and stereometric analysis of Langerhans cells in mouse epidermis

In the presented studies stereometric analysis and spatial reconstruction was performed on two Langerhans cell (LC) types. One was free of LC-I and the other contained LC-II Birbeck granules in the perinuclear space. The presented stereometric analysis demonstrated significant differences between the so-distinguished two cell types. Differences were observed not only in the number and distribution of Birbeck's granules but also in the areas of smooth and rough endoplasmic reticulum, in the area of vesicles surrounding Golgi apparatus, in the volume of cisterns of the apparatus, and in the ratio of cell nucleus area to its volume. Differences noted between the two cell types were of quantitative character. They might result from different stages of differentiation of the cells from their precursors in the epidermis or from distinct functional stages of the cells.

Antigen recognition in the female reproductive tract: I. Uptake of intraluminal protein tracers in the mouse vagina

Local immunization in the vagina of several species elicits immune responses, but little is known about the uptake, processing and recognition of antigens at this site. We investigated the uptake of intravaginally administered tracers using FITC-bovine albumin, FITC-horse ferritin and FITC-horseradish peroxidase in non-pregnant and pregnant mice. Tracers were detected in cells in the vaginal epithelium and stroma at diestrus, proestrus and metestrus, but not at estrus. During pregnancy, racers were present in vaginal cells on Day 6 but not on Day 13. The distribution of tracers in the vagina was the same in all mice. They were present in vaginal epithelium in cells similar to Langerhans' cells and in the stroma in cells that resembled dendritic cells, fibroblasts or macrophages. In some non-pregnant mice, tracers were present in cells adjacent to lymphatic nodules located in the adventitia between the vagina and urethra. Tracers were seen in phagocytic cells lining the marginal and medullary sinuses of the draining lymph nodes (iliac nodes) in some non-pregnant mice at 4 h after intravaginal administration, or in small, dendritic cells in the paracortex at 17 h. To test the possibility that transfer of proteins into the vagina was due to toxic effects of the tracers, FITC-conjugated proteins were also administered into the lumen of uterine horns, and their distribution in horns, cervix and vagina was studied. In uterine horns, tracers were either absent or were located only in apical vesicles in the luminal epithelium. Tracers were present in the cervix and vagina as described above for intravaginal tracers. This result suggests that uptake of tracers in the vagina was not due to toxic effects, and that the vagina and cervix are major sites of protein uptake into the reproductive tract.

Dendritic cells in contact sensitivity

Bone-marrow-derived DC, passing through the skin or residing there as LC, acquire antigen following epicutaneous exposure to contact sensitizer. They move as veiled cells in the afferent lymphatics and migrate to draining lymph nodes, where they become interdigitating cells of the paracortex. Here they initiate T-cell responses; the cytotoxic T cells and antibody formation which develop may be able to target on DC as well as other antigen-bearing cells, so producing feed-back mechanisms to switch off immune responses. Additional features include a systemic effect which leads to movement of DC without antigen into lymph nodes. What are the signals leading to this movement and what is its significance? There is evidence for synergy between directly haptenated DC and DC not directly acquiring antigen. How does this occur and how important is this effect in ensuring the potency of DC in presenting contact sensitizer to T cells? What is the importance of antigen processing by LC? Finally, dendriform cells which may be of T-cell origin are also present in the skin. What is their role in modulating the development of contact sensitivity?

Antigen presented in the local lymph node by cells from dimethylbenzanthracene-treated murine epidermis activates suppressor cells

Application to skin depleted of LC by treatment with the chemical carcinogen DMBA of a dose of contact sensitizer optimal for inducing contact sensitivity activates transferrable suppressor cells. Excision of solvent- or DMBA-treated skin at various times following application of the contact sensitizer DNFB indicated that the fraction of antigen which leaves the skin within the first few hours induces tolerance. An initial signal inducing unresponsiveness, observed within 1/2 hr, was overturned 3-6 hr later. A more permanent tolerogenic signal in the DMBA- but not solvent-treated lymph node resulted from an epidermal cell from DMBA-treated skin presenting antigen to suppressor cells. Therefore it is likely that suppressor cells are activated in DMBA-treated mice by an epidermal cell which migrates to the local lymph node. Local lymph node cells from DMBA-treated mice also have a diminished ability to present antigen in vivo but they do not activate suppressor cells.

Interface dermatitis in patients with the acquired immunodeficiency syndrome

We report twenty-five patients with the acquired immunodeficiency syndrome (AIDS) and interface dermatitis. Patients with AIDS and interface dermatitis had numerous opportunistic and herpetic infections. Nearly all patients were receiving at least one medication prior to the development of their rash and many were clinically thought to have a drug eruption. When compared to skin biopsy specimens from non-AIDS patients with drug eruptions, specimens from patients with AIDS and interface dermatitis demonstrated a greater degree of vacuolar change, the frequent occurrence of necrotic keratinocytes, often in clumps, and the absence of eosinophils and polymorphonuclear leukocytes in the dermal infiltrates. Histologic and clinical features of our patients with AIDS and interface dermatitis are presented and contrasted with other interface dermatitides. Systemic and cutaneous immune abnormalities in patients with AIDS may be relevant to the pathogenesis of this interface process.

Immunologic aspects of leprosy

Twenty seven cases of leprosy from Egypt were examined. Monocytes were found to be high in peripheral blood in lepromatous cases. The percentage of small lymphocytes in blood was increased in tuberculoid patients. The immunoglobulins were higher in all types of leprosy patients than in normal persons.

The ultrastructure of human gingival Langerhans cells in health and disease

There was a statistically significant shift towards increased proportions of type I Langerhans cells (containing many Langerhans-cell granules) and reduced proportions of both type II Langerhans cells (containing few granules) and indeterminate cells in diseased oral epithelium when compared to healthy oral epithelium. Langerhans cells and indeterminate cells were also seen in the sulcular epithelium of healthy and diseased specimens but never in junctional or pocket-lining epithelium.

Carcinogen-induced depletion of cutaneous Langerhans cells

The chemical carcinogen 7,12-dimethylbenz (a) anthracene (DMBA) is a potent carcinogen which, when applied to the skin of BALB/c mice weekly for 7-8 weeks, causes the induction of macroscopically visible skin tumours. We report that DMBA also depletes Langerhans cells (LC) from treated skin; the number of cutaneous LC is reduced by nearly 50% 3 days after the first application of DMBA, and continues to decrease upon further treatment. After 7-8 weeks of DMBA application, while tumours are becoming macroscopically visible, there is a considerably lower LC density in treated skin. Upon cessation of the DMBA treatment, the LC repopulate the skin, returning to control values within 55-64 days. During this repopulation of the skin by LC, the tumours begin to decrease in size. Since LC function as local cutaneous antigen-presenting cells, and are responsible for initiation of an immune response against antigens in the skin, their depletion during tumour induction may allow DMBA-transformed cells to circumvent the immune system and form tumours. Their reappearance associated with tumour regression suggests that the LC are involved in an immune response against the tumours.

Cervical healing and Langerhans' cells

A study of cervical epithelium healing after laser treatment found the early presence of Langerhans' cells. These cells were demonstrated using a histochemical technique for adenosine triphosphatase. The significance of Langerhans' cells in healing epithelium and their probable immunological role is discussed.

Lymphocyte subsets and Langerhans cells/indeterminate cells in erythema multiforme

A peroxidase-antiperoxidase study using monoclonal antibodies directed against T and B lymphocytes and Langerhans cells/indeterminate cells (LC/IC) was undertaken in order to understand more clearly the changes observed in erythema multiforme. At the various stages of development, from normal skin to target lesions, the quantity of inflammatory cells differed, but in each case the number of T8+ (cytotoxic/suppressor) cells was greater than the number of T4+ (helper/inducer) cells in the epidermis, whereas the latter exceeded the former in the dermis. Concomitant with the initial epidermis changes, there was an increase in the number of T6+ (LC/IC) cells in the upper and lower epidermis. With slight to moderate basal unit destruction, the number of LC/IC in the upper epidermis exceeded those in the lower epidermis. With severe basal unit destruction, there was a loss of LC/IC in the lower epidermis as detected by T6 reactivity. In fully formed blisters, the LC/IC in the upper half of the epidermis were decreased in parallel with the degree of epidermal necrosis. The character of the lymphocytic inflammatory infiltrate and redistribution in LC/IC are similar to those findings described in allergic contact dermatitis. The clinical, histologic, and immunopathologic changes in erythema multiforme appear to be due in part to cellular immune mechanisms with the lymphocyte as the predominant effector cell, and our data suggest a possible role for LC/IC in this disorder.

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.

Langerhans' cell tumor of the eyelid

Light microscopic examination of a cutaneous nodule excised from the eyelid of a 35 year-old woman showed a monotonous proliferation of histiocytes with pagetoid infiltration of the epidermis. Following excision of this lesion, ipsilateral cervical lympadenopathy was noted. An infiltrate of cytologically similar cells was found. Electron microscopic examination showed features of Langerhans' cells including typical Birbeck granules in tumor cells from the lymph nodes. It is suggested that this localized neoplasm originated in the skin and metastasized to the regional lymph nodes.

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

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

Ultrastructural studies of spontaneously regressing plane warts. Langerhans cells show marked activation

Ultrastructural changes in Langerhans cells during spontaneous involution of plane warts were examined. In areas with activated macrophages and epidermal cell interaction, Langerhans cells showed signs of enhanced cellular activity with an increased number of Langerhans cell granules, as in contact dermatitis. The fine structure of Langerhans cell granules, however, was unusual in that the vesicular portion was surrounded by a membrane, and this portion frequently occurred independently taking the shape of a loop.

A new morphologic manifestation of Langerhans cells in guinea pig corneal transplants

Langerhans cells are virtually never seen in the normal undisturbed corneal epithelium. They may be stimulated to migrate into the corneal epithelium by a variety of chemical and mechanical stimulation, including penetrating keratoplasty. We have found a previously undescribed morphologic manifestation of the Langerhans cell in guinea pig eyes undergoing corneal transplantation. These cells are found around the graft, and in high concentration around sutures. They may be a motile form of the typical Langerhans cell or a specialized form which captures or distributes antigen.

Eosinophilic granuloma of lymph nodes--a variant of histiocytosis X

A clinicopathologic study of histiocytosis X in lymph nodes disclosed a special variant: primary eosinophilic granuloma of lymph nodes. This variant involves one or more lymph nodes, but does not infiltrate any other organs. Histologically, the infiltration of lymph nodes by histiocytosis X cells and eosinophils is similar to that seen in disseminated or metastatic histiocytosis X. Most cases of eosinophilic granuloma of lymph nodes are recognizable as primary, however, by the heavy infiltration of the surrounding tissue. The predominant proliferating cells are histiocytosis X cells ('Langerhans cells'), which contain Birbeck granules on electron microscopy and are lysozyme-negative. The disease was found in 30 patients among a total of 64 cases of histiocytosis X collected at the Lymph Node Registry in Kiel. Primary eosinophilic granuloma of lymph nodes occurs predominantly in children and young adults and shows a slight preponderance of males. Clinically, the patients present with mostly afebrile and sometimes painful lymphadenopathy, which is more often solitary (in the cervical or inguinal region) than widespread. The erythrocyte sedimentation rate and/or serum alpha 2-globulin level are elevated in many patients. There may also be an increase in the number of leucocytes, especially eosinophils, in the blood. The prognosis is favourable: the lymphadenopathy disappeared spontaneously in most patients and only one patient developed two recurrences. Thus, primary eosophilic granuloma of lymph nodes is interpreted as a benign lesion. It might be a special reaction of the T cell system.

Adjuvant action of capsular polysaccharide of Klebsiella pneumoniae on antibody response. IX. Its effect on the histology of the regional lymph node and other lymphoid organs

The sequence of histological changes in the regional lymph node and other lymphoid organs of mice injected with the capsular polysaccharide of Klebsiella pneumoniae (CPS-K) or bacterial lipopolysaccharide (LPS) was followed. Injection of CPS-K, but not LPS, induced the following characteristic histological changes in the regional lymph node. In the early stage there was a marked decrease in the number of small lymphocytes, accompanied by the appearance of scattered fragmented nuclei and infiltration of polymorphonuclear neutrophilic leukocytes, and in the late stage there was marked proliferation of macrophage-like cells and pyroninophilic cells. Histological changes in the thymus and spleen and changes in cell populations in the bone marrow and peripheral blood after CPS-K injection were essentially the same as after LPS injection. Since CPS-K has a much stronger adjuvant action on antibody response than does LPS, it is suggested that the characteristic histological changes in the regional lymph node after injection of CPS-K are closely related to its extraordinarily strong adjuvant action.

Langerhans cells as macrophages in skin and lymphoid organs

Properties of epidermal Langerhans cell were compared with those of a number of other dendritic cells in lymphoid organs and of mononuclear phagocytes. Among the dendritic "reticulum" cells included were indeterminate cells from the epidermis, interdigitating "reticulum" cells from T-dependent areas of lymphoid tissue and thymus, follicular dendritic cells of Nossal, and the dendritic cells described by Steinman and Cohn. Interdigitating cells with typical Birbeck granules, in the thymus and in the paracortices of lymph nodes, which are morphologically indistinguishable from Langerhans cells and indeterminate dendritic cells in the epidermis, appear to belong to the same system and possibly represent a subpopulation of "macrophages." On the basis of their similarity to these other dendritic cells, we believe Langerhans cells may function in antigen presentation, lymphokine production, provision of a microenvironment for T lymphocytes, and prostaglandin secretion.

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.

Pathopysiological aspects of immune complex diseases. Part II. Phagocytosis, exocytosis, and pathogenic depositions

Elimination of IC by the phagocytic system occurs mainly by macrophages and contrarotates to the pathogenic effect. Decisive to prevent systemic IC disease is the capacity of the phagocytic system. In the case of its saturation, the danger of the occurrence of IC disease is greatly enhanced. Conclusive evidence seems to exist that IC of extremely small or extremely high lattice structure (precipitates) are less pathogenic than soluble IC of medium network. Small IC in extreme antigen and antibody excess or precipitates exhibit a reduced complement activating potency. Small IC in extreme antigen or antibody excess hardly interact in vitro with membrane receptors and do not induce IC disease when injected or formed in vivo. Highly lattices IC, especially precipitates, are eliminated extremely quickly from the circulation, mainly by macrophages and there deposition in the kidney is significantly reduced. Thus, lack of quality of the antibody to precipitate the antigen and a reduced capacity and effectivity of the phagocytic system to eliminate the IC may be extremely important in the generation of IC diseases. Facing the overwhelming and partly even inconsistant data of this topic, one may doubt whether IC diseases may be regarded to be a defined and coherent disease. Too many variables and questions exist concerning the nature of the antigen, especially in tumor and autoimmune diseases, concerning the quality of the antibody and the characteristics of the pathogenic IC and concerning localization and the elimination process. Nevertheless, common pathophysiological pathways of IC diseases may be recognized.

Surface densities of Langerhans cells in relation to rodent epidermal sites with special immunologic properties

Epidermal Langerhans cells bear surface receptors which implicate them as immunocompetent cells and they are now felt to play an important role both in delayed hypersensitivity and in skin allograft reactions. To determine the relationship between Langerhans cell availability and certain immunologic phenomena, surface densities were determined by ATP-ase and gold uptake in 3 rodent species: guinea pig, hamster, and mouse. Surface densities in epidermal specimens from the ear, back, foot pad, and buccal mucosa varied between 600 and 1500 cells/mm2. Significantly fewer cells were found in the hamster cheek pouch (130 cells/mm2) and in the mouse tail (110 cells/mm2 for C57BL/6J; 260 cells/mm2 for BALB/c nu/nu). Langerhans cells were absent from the central port;on of the cornea in all 3 species. Decreased Langerhans cell surface density may contribute to immunologic privilege as has been observed for the cornea and hamster cheek pouch and to the unusual allograft characteristics of mouse tail skin.

Target role of Langerhans cells in mycosis fungoides: transmission and immuno-electron microscopic studies

Langerhans cells of the epidermis are "special" macrophages, as indicated by their expression of Fc and C3 receptors and Ia antigen. Functionally, they can replace macrophages in presentation of antigens to T cells and in the MLR. Ultrastructural and immunologic studies were carried out on epidermal samples of mycosis fungoides. As in contact allergy, apposition of lymphocytes to Langerhans cells was noted. Destruction of Langerhans cells appeared to act as the focus for the development of Pautrier microabscesses. This destruction was accompanied by ingress of histocytic cells, probably related to the stem cell population for Langerhans cells. The target cell role of Langerhans cells appears to be similar in contact allergy and mycosis fungoides.

Ia antigens on indeterminate cells of the epidermis: immunoelectronmicroscopic studies of surface antigens

An antiserum against human B-lymphoblastoid cell membrane alloantigens (Ia-like antigens) was used to study the presence of such antigens on dendritic cells in human epidermis. Only Langerhans cells and the majority (85%) of so-called indeterminate cells were positively stained, as shown by immuno-electron microscopy. Fifteen percent of the indeterminate cells were negative and were considered to be immature melanocytes. A relationship exists between the indeterminate cell and the Langerhans cell. A proposal is made concerning emigration of Langerhans cells in response to haptenic stimulation, and the immigration of indeterminate cells to restore the status quo.