Antigen-presenting capacity in normal human dermis is mainly subserved by CD1a+ cells

Dermal dendrocytes FXIIIa+ are essential antigen-presenting cells in indeterminate leprosy

Indeterminate leprosy (IL) is the early phase of Hansen disease and reword (APCs). Langerhans cells and dermal dendrocytes FXIIIa positive (DDFXIIIa) are the major APCs in the skin and can be identified by the expression of CD1a and FXIIIa, respectively, by immunohistochemical techniques. Plasmacytoid dendritic cells (PDCs) are another type of dermal dendrocytes with a questionable antigen-presenting function and can be highlighted by anti-CD123 expression. To our knowledge, there are no studies evaluating DDFXIIIa and PDC in IL. The purpose was to investigate the involvement of these cells in the pathogenesis of IL. The authors performed a retrospective study on 18 cases of IL (10 confirmed and 8 suspected) to investigate expression of FXIIIa, CD1a, and CD123. The results were compared with normal skin (for CD1a and FXIIIa only). A higher amount of FXIIIa-positive cells (P , 0.05) in confirmed and suspected IL cases was noted when comparing with normal skin. However, CD1a showed no quantitative differences in the epidermis of IL lesions when comparing with normal skin and CD123 expression was negligible. Based on these findings, the authors postulate that Langerhans cells and PDCs do not have a major role in IL and that DDFXIIIa may be the main APCs in IL. Further study is required to establish this.

An improved cell isolation method for flow cytometric and functional analyses of cutaneous wound leukocytes

Isolation of leukocytes from full-thickness excisional wounds has proven to be a difficult process that results in poor cell yield and holds significant limitations for functional assays. Given the increased interest in the isolation, characterization and functional measurements of wound-derived cell populations, herein we describe a method for preparing wound cell suspensions with an improved yield that enables both phenotypic and functional assessments.

A study of dendritic cell and MHC class II expression in dogs with immunomodulatory-responsive lymphocytic-plasmacytic pododermatitis

The term immunomodulatory-responsive lymphocytic-plasmacytic pododermatitis (ImR-LPP) has previously been proposed to denote a sub-population of dogs with idiopathic pododermatitis. The objective of this study was to investigate dendritic cell (DC) and MHC class II antigen expression in lesional skin of dogs with ImR-LPP (n=47). Median epidermal CD1c(+) cell counts were 37.8 and 12.5 mm(-1) in ImR-LPP dogs and healthy controls (n=27), respectively (P<0.01), while the corresponding dermal cell counts were 180.9 and 45.0 mm(-2), respectively (P<0.01). Intra-epidermal clusters of DCs were observed in 18/47 dogs with ImR-LPP. Median epidermal MHC class II(+) cell counts were 32.5 and 10.5 mm(-1) in ImR-LPP dogs and healthy controls, respectively (P<0.01), while the corresponding dermal cell counts were 216.9 and 46.9 mm(-2), respectively (P<0.01). Dermal MHC class II(+) staining was primarily associated with DCs (47/47 dogs), mononuclear inflammatory cells (45/47), fibroblast-like cells (19/47) and vascular endothelium (14/47). The DC hyperplasia and increased MHC class II expression in lesional ImR-LPP skin are consistent with enhanced antigen presentation, and suggest that both parameters may contribute to the pathogenesis of ImR-LPP through the priming and activation of CD4(+) T cells. Equally, it is possible that the enhanced DC numbers observed in this study may contribute to the immunoregulation of steady-state pathology in lesional ImR-LPP skin through additional expanded, although as yet unresolved, mechanisms.

Effect of PUVA, narrow-band UVB and cyclosporin on inflammatory cells of the psoriatic plaque

BACKGROUND

Because antigen presenting is necessary for T-cell activation, antigen-presenting cells should be involved in the pathogenesis of psoriasis. In this study, our purpose was to evaluate and compare effects of PUVA, cyclosporine A and narrow-band UVB on dendritic cells and activated lymphocytes in the psoriatic lesions.

METHODS

Forty-five volunteered patients (15 patients in each treatment group as PUVA, cyclosporin A and narrow-band UVB) were enrolled in this study. Lesional skin biopsies were taken from each patient before and after treatments. Fresh frozen biopsies were studied for the expressions of CD1a, CD68, CD86, CD4, CD8 and HLA-DR proteins by immunohistochemistry.

RESULTS

There was no correlation between severity of the lesions and expressions of the antigens. Only PUVA significantly decreased CD1a+ epidermal Langerhans cells' (LCs) counts. Treatment modalities decreased expression of costimulator CD86, and most of them decrease antigen-presenting capacity of skin by decreasing HLA class-II expression.

CONCLUSIONS

All treatment modalities equally reduce lymphocytes, macrophages and dendritic cells. PUVA is the only treatment that decreases epidermal LCs. All treatments effectively diminish expression of CD86 and inhibit this step of inflammation.

UVA Radiation Impairs Phenotypic and Functional Maturation of Human Dermal Dendritic Cells

There is now strong evidence that the ultraviolet A (UVA) part of the solar spectrum contributes to the development of skin cancers. Its effect on the skin immune system, however, has not been fully investigated. Here, we analyzed the effects of UVA radiation on dermal dendritic cells (DDC), which, in addition, provided further characterization of these cells. Dermal sheets were obtained from normal human skin and irradiated, or not, with UVA at 2 or 12 J per cm2. After a 2 d incubation, the phenotype of emigrant cells was analyzed by double immunostaining and flow cytometry. Results showed that migratory DDC were best characterized by CD1c expression and that only few cells co-expressed the Langerhans cell marker Langerin. Whereas the DC extracted from the dermis displayed an immature phenotype, emigrant DDC showed increased expression of HLA-DR and acquired co-stimulation and maturation markers. We showed here that UVA significantly decreased the number of viable emigrant DDC, a process related to increased apoptosis. Furthermore, UVA irradiation impaired the phenotypic and functional maturation of migrating DDC into potent antigen-presenting cells, in a concentration-dependent manner. The results provide further evidence that UVA are immunosuppressive and suggest an additional mechanism by which solar radiation impairs immune response.

Human papillomavirus molecular biology and pathogenesis

Human papillomavirus (HPV) infection is the most common sexually transmitted disease in the world and accounts for an estimated 11% of the global cancer incidence in women. HPV-16 is the most prevalent type detected in cervical cancer and along with types 18, 31, 33 and 45 has been classified as a class I carcinogen. In addition to cervical cancer, HPVs are also associated with the malignant transformation of other mucosal and skin cancers. Thus, the combination of the malignant potential of HPV and its high prevalence of infection confers to it an importance of generalized clinical and virological significance. The natural history of HPV infection with or without treatment varies from spontaneous regression to persistence. The most important mechanism for wart regression appears to be cell-mediated immunity. Cytokines released by keratinocytes or cells of the immune system may play a part in the induction of an effective immune response against HPV infection and the subsequent regression of lesions. This review discusses the molecular biology, pathogenesis and immunology of HPV infections.

Phenotypic and functional outcome of human monocytes or monocyte-derived dendritic cells in a dermal equivalent

The dermis harbors a true dendritic cell population that could elicit primary allogeneic T cell responses in vitro and contact hypersensitivity reactions in vivo. The origin of dermal dendritic cells remains poorly understood, however. In this study, we analyzed the fate of monocytes or monocyte-derived dendritic cells in a dermal equivalent. Freshly isolated monocytes or monocytes cultured for 6 d with either GM-CSF/IL-4 or GM-CSF/IL-4/TGF-beta 1 (TGF-DC) were seeded in a collagen solution with normal human fibroblasts. The lattices were cultured for 7--14 d in the presence, or absence, of the exogenous cytokines, before phenotypic and functional studies were performed. Supply of exogenous cytokines allows the appearance of typical CD1a(+)/CD14(-)/CD68(low) dendritic cells with significant allostimulatory property, regardless of the cell type incorporated into the lattices. In cytokine-free conditions, monocytes and GM-CSF/IL-4-derived dendritic cells give rise to a CD1a(-)/CD14(+)/CD68(high) monocyte/macrophage population with no allostimulatory property. When incorporated into the lattices in the absence of exogenous cytokines the TGF-DC express few CD68 and FXIIIa. Interestingly, these cells do not all convert into the CD14(+)/CD1a(-) population. Indeed, a small HLA-DR(+)/CD1a(+)/CD14(-) subset was consistently found, which represents about one-third of the HLA-DR(+) cells. Moreover, TGF-DC recovered from the lattices after culture without cytokines do display a significant allostimulatory function. Thus, in the absence of exogenous cytokines, only Langerhans-cell-like dendritic cells can retain the typical dendritic cell features when inserted in a dermal environment. Taken together, these results may provide evidence supporting an epidermal origin of dermal dendritic cells.

Nonlymphoid intraepidermal mononuclear cell collections (pseudo-Pautrier abscesses): a morphologic and immunophenotypical characterization

We evaluated the incidence, morphology, and immunophenotype of intraepidermal collections of mononuclear cells (ICMC) in a large number of inflammatory dermatosis and cutaneous lymphomas. ICMC appeared as small to large aggregates of cells, showing a morphology variable from monocytes to obvious dendritic cells, admixed with rare lymphocytes. ICMC were recognized in the epidermis or within hair follicle epithelium, and were either loosely or compactly arranged. ICMC were identified in 124 of 1,248 skin biopsies (9.9%) of inflammatory or lymphoid infiltrates, and were particularly frequent in spongiotic (43.4%) and in lichenoid dermatitis (10%), whereas they were rarely found in nonspecific superficial dermatitis (3.8%) and in psoriasis (4.7%). ICMC were also frequent in cutaneous T-cell lymphoma (13.3%), where they mimicked Pautrier abscesses. The ICMC forming cells showed a unique phenotype: the majority of them expressed CD1a and S-100, and lacked CD14, similar to mature Langerhans cells, but they were also strongly labeled by anti-CD11b, anti-CD36, and anti-CD68. Moreover, a subpopulation of them expressed CD83, an antigen that is usually absent on Langerhans cells. The occurrence of ICMC is a rather frequent, although hitherto poorly studied, phenomenon, occurring in several dermatosis, but particularly frequent in spongiosis-associated skin reactions. The cells within ICMC are represented by dendritic cells and dendritic cell precursors, whose phenotype indicates their derivation from circulating monocytes and differentiation into mature Langerhans cells.

Canine cutaneous and systemic histiocytosis: reactive histiocytosis of dermal dendritic cells

Canine histiocytic proliferative disorders include reactive diseases such as cutaneous and systemic histiocytosis and neoplastic diseases such as cutaneous histiocytoma and localized and disseminated histiocytic sarcoma (malignant histiocytosis). Their etiology and pathogenesis are unknown. Canine cutaneous and systemic histiocytosis target the skin and subcutis and have similar clinical behavior. Systemic histiocytosis also affects other organ systems. Clinicopathologic and phenotypic features of canine cutaneous and systemic histiocytosis were examined in this study. Canine cutaneous (18 cases) and systemic (26 cases) histiocytosis were characterized by angiocentric, pleocellular accumulations consisting of CD1+, CD11c+, MHCII+, CD4+, and Thy-1+ (CD90) activated dermal dendritic antigen-presenting cells (APC) with admixed CD3+, CD8+, TCRalphabeta+ T lymphocytes, and neutrophils. Hence, canine cutaneous and systemic histiocytosis represent two clinical manifestations of a reactive proliferation of dermal dendritic cells. Cultures and special stains failed to identify infectious agents. Canine reactive histiocytoses respond to immunosuppressive therapy (cyclosporine A or leflunomide). Therefore, immune-dysregulatory mechanisms are likely to be involved. Spontaneous reactive histiocytoses are frequently seen in dogs, and they constitute an excellent model to study pathologic mechanisms involved in reactive proliferations of dermal dendritic APC.

Immunological activation of dermal Langerhans cells in contact with lymphocytes in a model of human inflamed skin

Langerhans cells play an important role in the skin's immune system. Little is known, however, about the antigen-presenting capacity of Langerhans cells in the context of skin inflammation. By immunohistochemistry we investigated the phenotypic characteristics of epidermal and dermal Langerhans cells and their spatial relationship with infiltrating lymphocytes. We studied skin flaps autotransplanted to the oral cavity to fill a defect after maxillofacial cancer surgery. In 15 of 21 cases sampled for the present study, the skin flaps were severely inflamed by Candida albicans infection. In contrast to the normal skin, such inflamed skin showed a marked increase in CD1a(+) dermal Langerhans cells. Double immunohistochemistry revealed that dermal Langerhans cells abundantly expressed B7-2 (CD86), a representative costimulatory molecule, and CD83, a marker of mature dendritic cells. Furthermore, these dermal Langerhans cells were in close contact with CD4(+)/CD45RO(+) lymphocytes. This cell-to-cell contact was further visualized by immunoelectron microscopy. Langerhans cells were also observed within lymphatic vessels that were identified by the expression of vascular endothelial growth factor receptor-3. Ki-67 labeling indices were 4.2% in CD4(+) T cells and 0.8% in CD8(+) T cells within the dermis. Factor XIIIa(+) dermal dendrocytes were distributed outside the clusters of lymphocytes and were not in contact with them. Our observations indicate that dermal Langerhans cells in the inflamed skin are activated to express common phenotypes to mature dendritic cells so that they could stimulate neighboring memory CD4(+) T cells.

Dendritic cells: role in skin diseases and therapeutic applications

Dendritic cells have entered the centre stage of applied immunological research. Dermatologists knew for quite some time about the extraordinary capacity of these cells to induce immune responses. Recent progress in using these cells as potent adjuvant for the treatment of human cancer has inaugurated an unprecedented wave of publications about the role of these cells for the pathogenesis and treatment of various types of cancers and infectious diseases. This short review attempts to follow some of the origins of dendritic cell research with special regard to dermatology and gives a perspective on newer developments such as the use of dendritic cells to induce antigen-specific tolerance.

Dermal dendritic cells associated with T lymphocytes in normal human skin display an activated phenotype

The CMRF-44 and CD83 (HB15) antigens are associated with functional maturation and activation of blood dendritic cells (DC). We describe the expression of these antigens on freshly isolated epidermal Langerhans cells and dermal DC as well as the distribution of CD83+/ CMRF-44++-activated DC within sections of normal human skin. Fresh Langerhans cells were prepared by standard techniques and large numbers of enriched (25%-55%), viable dermal DC were obtained using an improved collagenase treatment protocol with density gradient enrichment. Freshly isolated Langerhans cells and dermal DC had similar costimulator and activation antigen expression, and both stimulated moderate levels of allogeneic T lymphocyte proliferation as determined in the 7 d mixed leukocyte reaction. In situ labeling of DC within skin sections revealed a population of CD83 and CMRF-44 positive dermal cells of which most (approximately 75%) were in intimate contact with CD3+ T lymphocytes, especially in the adnexal regions. In contrast, only 25%-30% of the more numerous CD1a++ dermal DC population were directly apposed to T lymphocytes. The CMRF-44++ dermal DC population stimulated an allogeneic mixed leukocyte reaction, confirming their identity as DC. These data, plus comparative data obtained for migratory dermal DC, suggest that only a small proportion of dermal DC have been triggered to a more advanced state of differentiation or activation. The striking association of the activated dermal DC population with T lymphocytes suggests that communication between these two cell types in situ may occur early in the immune response to cutaneous antigen.

Quantitative immunohistochemical differences in Langerhans cells in dermatitis due to internal versus external antigen sources

Cutaneous hypersensitivity reactions can develop against antigens delivered through the epidermis (contact dermatitis) or through the blood vessels (e.g., drug eruptions). On routine histology alone, it is not always possible to determine the route of the antigen. Langerhans cells (LC) are the main antigen-presenting cells in contact dermatitis. Dermal dendrocytes (DC) are antigen-presenting cells and may be involved in dermal reactions. We tested the hypothesis that there is a difference between dermatitis due to external and internal antigen sources with regard to the number or function of LC and DC. In 85 cases of dermatitis, numbers of S100 and HLA-DR reactive cells per linear millimetre of epidermis were counted. The amount of epidermal spongiosis was evaluated qualitatively. In 35 cases, the number of DC per mm2 (as defined by Factor XIIIa expression) was evaluated. The patients were then divided into two groups based on whether the final clinical evaluation considered the dermatitis to be secondary to an external (35 cases) or internal antigen (50 cases). Dermatitis due to external antigens had significantly more LC/mm and more frequent HLA-DR expression than dermatitis due to internal antigens, mean +/- SEM; 21.2+/-2.04 vs. 9.1+/-1.02 (p<0.00001) and 16.3+/-2.49 vs. 6.0+/-0.92 (p=0.0001), respectively. Spongiosis was more marked in external antigen cases. DC were more numerous in internal than in external antigen cases, but the differences were not statistically significant. In our model, determination of numbers of LC/mm is the variable with the highest power to discriminate between internal and internal sources. Quantification of HLA-DR+ LC and degree of spongiosis provide little additional discriminatory power.

Human dermal dendritic cells process and present soluble protein antigens

Recently, a novel type of dendritic antigen-presenting cell has been identified in the dermis of normal human and mouse skin. These dermal dendritic cells (DDC) occur in higher numbers than epidermal Langerhans cells, represent a distinct differentiation pathway of dendritic cells, and are as potent as Langerhans cells in the activation of superantigen specific T cells. As yet, nothing is known about their capacity to take up, process, and present soluble protein antigens. We used the model of tetanus toxoid (TT) driven T cell proliferation to address these questions. To test for active internalization of TT protein, gold labeled TT was incubated with Langerhans cells and DDC and could be traced to multivesicular endo-lysosomal compartments. DDC internalize TT through a receptor-mediated, clathrin-independent pathway, whereas Langerhans cells predominantly use macropinocytosis. To verify that DDC process TT by the exogenous pathway of antigen presentation, we pulsed DDC with TT protein or TT peptide after preincubation with chloroquine. Preincubation with chloroquine diminished the capacity of DDC to induce TT protein specific T cell proliferation (70-80%), but was not effective to suppress TT peptide induced T cell responses. DDC were as potent as Langerhans cells and 5-10 x more potent than plastic adherent monocytes in the presentation of TT to autologous resting T cells. Furthermore, as few as 50 DDC (stimulator:responder ratio of 1:1000) were able to induce a significant TT specific T cell proliferation. Because a subpopulation of DDC expresses low levels of CD1a, a phenotypic marker of Langerhans cells, sorting of CD1a positive and negative DDC was performed. On a per cell basis, CD1a positive and negative DDC were equally potent at mediating TT specific T cell proliferation. Thus, DDC are able to internalize, process, and present soluble protein antigens such as TT and may therefore play an important role in the regulation of skin immune responses.

High-affinity immunoglobulin E receptor (Fc epsilon RI)-bearing eosinophils, mast cells, macrophages and Langerhans' cells in allergen-induced late-phase cutaneous reactions in atopic subjects

We have used in situ hybridization (ISH) and immunohistochemistry (IHC) to investigate the kinetics of the expression for Fc epsilon RI mRNA (alpha-, beta- and gamma-chains), the alpha-chain protein product, as well as the phenotype of the mRNA- or protein-positive cells in allergen-induced late-phase skin reactions in atopic subjects. Compared with diluent controls, there were significant increases in the total number of mRNA+ cells for the alpha-, beta- and gamma-chains for Fc epsilon RI at all time-points (6, 24 and 48 hr) after allergen challenge (P < 0.01). By double IHC/ISH significant increases in alpha-, beta- and gamma-chain mRNA+ macrophages, eosinophils, mast cells and CD1a+ cells were also observed after allergen challenge (P < 0.05). The distribution of Fc epsilon RI subunit (alpha-, beta-, or gamma-chain) mRNA+ co-localization was CD68+ macrophages (42-47%), EG2+ eosinophils (33-39%), tryptase+ mast cells (5-11%) and CD1a+ Langerhans' cells (2-4%). Using single IHC, significant increases in the total number of Fc epsilon RI protein+ cells (P < 0.01) were observed 24 and 48 hr after allergen challenge. Double IHC showed that the distribution of Fc epsilon RI+ cells was tryptase+ mast cells (33%), CD68+ macrophages (36%), EG2+ eosinophils (20%), CD1a+ Langerhans' cells (4%) and unidentified cells (7%), at the 24-hr allergen-challenged sites. These observations suggest that the cutaneous late-phase reaction in man is associated with up-regulation of Fc epsilon RI on eosinophils, macrophages, mast cells and Langerhans' cells.

CD101 is expressed by skin dendritic cells. Role in T-lymphocyte activation

CD101 was first described in our laboratory using two different monoclonal antibodies, BA27 and BB27, recognizing a 140-kDa disulfide-bonded homodimeric polypeptide on a small subset of circulating T lymphocytes and on most activated T cells in vitro. Further, it has been reported that most intestinal mucosal T lymphocytes expressed CD101. The gene coding for the CD101 antigen has been cloned and found to be identical to the gene coding for the recently described V7 antigen, corresponding to a type I trans-membrane protein with seven immunoglobulin-like loops in its extracellular domain. To define surface proteins that are involved in skin dendritic cell (DC) localization or function, we looked for the expression of CD1O1 on skin DC migrating from human skin explants. The majority of these DC had a phenotype of Langerhans cell (LC)-like mature DC, i.e., HLA-DR+ CD1a+ CD1c+ CD11a+ CD11c+ CD40+ CD50+ CD54+ CD58+ CD80+ CD83+ CD86+. We found that CD101 was expressed by a major subset of these HLA-DR+ CD1a+ CD1c+ LC-like skin DC. Next, we studied the effect of anti-CD101 monoclonal antibodies on primary allogeneic and on soluble antigen-specific mixed skin DC-lymphocyte reactions. We showed that two different monoclonal antibodies, BB27 and V7.1, inhibited the T-lymphocyte proliferative responses and that the inhibitory effect was overcome by high doses of exogenous IL-2. As both DC and T lymphocytes expressed CD101 molecules, we determined that the inhibitory effect was achieved both at the responder T-cell level and at the DC level. Thus, CD101 which is expressed on a subset of circulating T lymphocytes, has also been found on a subpopulation of LC-like DC. This molecule plays a major role in the activation of T cells by skin DC.

Pattern of cytokine receptors expressed by human dendritic cells migrated from dermal explants

Different reasons account for the lack of information about the expression of cytokine receptors on human dendritic cells (DC): (a) DC are a trace population; (b) the proteolytic treatment used to isolate DC may alter enzyme-sensitive epitopes; and (c) low numbers of receptors per cell. In the present work the expression of cytokine receptors was analysed by flow cytometry on the population of dermal DC (DDC) that spontaneously migrate from short-term culture dermal explants. DDC obtained after dermal culture were CD1alow, CD1b+, CD1c+, human leucocyte antigen (HLA)-DR+, CD11chigh, CD11b+ and CD32+. The DC lineage was confirmed by ultrastructural analysis. DDC expressed interleukin (IL)-1R type 1 (monoclonal antibody (mAb) hIL-1R1-M1; and 6B5); IL-1R type 2 (mAb hIL-1R2-M22); IL-2R alpha chain (mAb anti-Tac; and hIL-2R-M1) and IL-2R gamma chain (mAb 3B5; and AG14C). DDC did not stain for IL-2R beta chain using four mAbs recognizing two different epitopes of IL-2R beta (mAb 2R-B; Mik-beta 1; and CF1; Mik-beta 3, respectively). DDC were also positive for the cytokine binding chains (alpha chains) of IL-3R (mAb 9F5); IL-4R (mAb hIL-4R-M57; and S456C9); and IL-7R (mAb hIL-7R-M20; and R3434). DDC showed low levels of IL-6R alpha chain (mAb B-F19; B-R6; and B-E23) and its signal transducer gp130 (mAb A2; and B1). DDC strongly expressed interferon-gamma receptor (IFN-gamma R) (mAb GIR-208) and were negative for IL-8R (mAb B-G20; and B-F25). All DDC were highly positive for granulocyte-macrophage colony-stimulating factor receptor (GM-CSFR) alpha chain (mAb hGM-CSFR-M1; SC06; SC04, and 8G6) and to a lesser extent for the common beta chain of GM-CSFR, IL-3R and IL-5R (mAb 3D7). On the other hand, reactivity was not found for granulocyte colony-stimulating factor receptor (G-CSFR) (mAb hGCSFR-M1) nor macrophage colony-stimulating factor receptor (M-CSFR) (mAb 7-7A3-17) confirming the DC lineage of DDC. As previously reported for lymphoid DC, DDC expressed tumour necrosis factor receptort (TNFR) 75000 MW (mAb utr-1; hTNFR-M1; and MR2-1) but lacked TNFR 55000 MW (mAb htr-9; MR1-1; and MR1-2). In summary, DDC express receptors for a broad panel of cytokines, even receptors for cytokines whose effects on DC are still unknown (i.e. IL-2R alpha gamma; IL-6R alpha/gp 130; IL-7R alpha gamma).

Langerhans cell hyperplasia and IgE expression in canine atopic dermatitis

Langerhans cells appear to be critical for IgE-mediated allergen capture and presentation in human atopic dermatitis. The present study sought to determine whether epidermal (i.e Langerhans cells) and dermal dendritic cells in the skin of dogs with atopic dermatitis are hyperplastic and expressed surface IgE. Frozen sections of lesional or non-lesional atopic and normal control canine skin were immunostained with CD1a-, CD1c-, and IgE-specific monoclonal antibodies. The enumeration of cells was performed by morphometry in both the epidermis and the dermis. Cell counts were compared with each individual's total serum IgE levels. Higher numbers of epidermal and dermal dendritic cells were present in atopic dogs than in normal control animals. Epidermal Langerhans cell counts were significantly higher in lesional than in non-lesional atopic specimens. IgE+ dendritic cells were observed in lesional atopic epidermis and dermis, and non-lesional atopic dermis, but not in normal control skin specimens. The percentages of IgE+ dendritic cells were correlated with each patient's total serum IgE levels. These results demonstrate dendritic cell hyperplasia and IgE expression in canine atopic dermatitis. Increased epidermal Langerhans cell counts in lesional specimens suggest an epidermal allergen contact in canine atopic dermatitis.