The role of dendritic cells in cutaneous immunity

Resolution of epoetin-induced pure red cell aplasia, successful re-challenge with roxadustat

The application of erythropoietin (EPO) can bring about a rare but serious complication called anti‐EPO antibody‐mediated pure red cell aplasia (PRCA). Once the disease is diagnosed, EPO administration should be stopped immediately. However, after the removal of the anti‐EPO antibody, treating anaemia in these patients with chronic renal disease with EPO therapy is difficult, as restarting EPO therapy risks the recurrence of anti‐EPO antibody‐mediated PRCA. A 26‐year‐old man with anaemia related to renal failure, who was administered recombinant human EPO subcutaneously, developed anti‐EPO antibody‐mediated PRCA. After removal of antibodies by treatment with corticosteroids and cyclosporine, therapy for anaemia of chronic renal disease with roxadustat achieved good results. Roxadustat is a new type of drug for the treatment of anaemia, and it can stimulate endogenous EPO within or near the physiologic range and increase haemoglobin levels.

Proteomic characterization of skin and epidermis in response to environmental agents

The skin and its outer epidermis layer in particular, prevent access of various environmental agents including potential allergens, irritants, carcinogens, ultraviolet radiation and microbes. Cells in the epidermis make a significant contribution to innate as well as adaptive immune reactions in skin. The skin immunity thus provides a biologic defense in response to hazardous environmental agents. Although proteomics has been utilized to establish skin proteomes and investigate skin responses to some environmental agents, it has not been extensively used to address the complexity of skin responses to various environments. This review summarizes cutaneous genes and proteins that have been characterized as related to skin exposure to environmental agents. In parallel, this review emphasizes functional proteomics and systems biology, which are believed to be an important future direction toward characterizing the skin proteome-environmental interaction and developing successful therapeutic strategies for skin diseases caused by environmental insults.

Pituitary adenylate cyclase-activating peptide and vasoactive intestinal polypeptide bias Langerhans cell Ag presentation toward Th17 cells

Epidermal Langerhans cells (LCs) are dendritic APCs that play an important role in cutaneous immune responses. LCs are associated with epidermal nerves and the neuropeptides vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) inhibit LC Ag presentation for Th1-type immune responses. Here, we examined whether PACAP or VIP modulates LC Ag presentation for induction of IL-17A-producing CD4(+) T cells. Treatment with VIP or PACAP prior to in vitro LC Ag presentation to CD4(+) T cells enhanced IL-17A, IL-6, and IL-4 production, decreased interferon (IFN)-γ and interleukin (IL)-22 release, and increased RORγt and Gata3 mRNA expression while decreasing T-bet expression. The CD4(+) T-cell population was increased in IL-17A- and IL-4-expressing cells and decreased in IFN-γ-expressing cells. Addition of anti-IL-6 mAb blocked the enhanced IL-17A production seen with LC preexposure to VIP or PACAP. Intradermal administration of VIP or PACAP prior to application of a contact sensitizer at the injection site, followed by harvesting of draining lymph node CD4(+) T cells and stimulation with anti-CD3/anti-CD28 mAbs, enhanced IL-17A and IL-4 production but reduced production of IL-22 and IFN-γ. PACAP and VIP are endogenous mediators that likely regulate immunity and immune-mediated diseases within the skin.

Percutaneous toxicity of dinitrochlorobenzene (DNCB) in rats

Contact hypersensitivity reaction (CHS) is a T-cell-mediated skin inflammatory reaction to cutaneous exposure to small sensitizing chemicals, haptens. While the significance of local inflammatory skin response to the hapten application in CHS induction and expression is known, there is paucity of data concerning systemic inflammation in CHS. In this study, changes in cellular (peripheral blood granulocytes) and humoral (plasma tumor necrosis factor (TNF)-α levels) components of inflammation during sensitization of rats with two consecutive applications of dinitrochlorobenzene (DNCB) were examined. The impact of sensitization on these parameters was determined by employing low (0.4%) and high (4%) hapten doses and by examining the dynamics (i.e. one and three days following the last application of DNCB) of these changes. Dose-dependent increase in relative numbers and priming (for respiratory burst and adhesion) effect of skin sensitization with DNCB on peripheral blood neutrophils in rats were noted. No changes in circulating TNF-α levels were observed following the sensitization. The increase in lung myeloperoxidase content and histologically evident presence of neutrophils was observed in lungs of the sensitized rats. The changes in granulocyte priming for adhesion might have accounted for the observed increase in lung neutrophil content in the sensitized rats.

Calcitonin gene-related peptide biases Langerhans cells toward Th2-type immunity

Langerhans cells (LC) are epidermal dendritic cells capable, in several experimental systems, of Ag-presentation for stimulation of cell-mediated immunity. LC have been considered to play a key role in initiation of cutaneous immune responses. Additionally, administration of donor T cells to bone marrow chimeric mice with persistent host LC, but not mice whose LC have been replaced by donor cells, exhibit marked skin graft-vs-host disease, demonstrating that LC can trigger graft-vs-host disease. However, experiments with transgenic mice in which regulatory elements from human langerin were used to drive expression of diphtheria toxin, resulting in absence of LC, suggest that LC may serve to down-regulate cutaneous immunity. LC are associated with nerves containing the neuropeptide calcitonin gene-related peptide (CGRP), and CGRP inhibits LC Ag-presentation in several models including presentation to a Th1 clone. We now report that CGRP enhances LC function for stimulation of Th2 responses. CGRP exposure enhanced LC Ag presentation to a Th2 clone. Upon presentation of chicken OVA by LC to T cells from DO11.10 chicken OVA TCR transgenic mice, pretreatment with CGRP resulted in increased IL-4 production and decreased IFN-gamma production. CGRP also inhibited stimulated production of the Th1 chemokines CXCL9 and CXCL10 but induced production of the Th2 chemokines CCL17 and CCL22 by a dendritic cell line and by freshly obtained LC. Changes in production of these chemokines correlated with the effect of CGRP on mRNA levels for these factors. Exposure of LC to nerve-derived CGRP in situ may polarize them toward favoring Th2-type immunity.

Characteristics of resident dendritic cells in various regions of rat periodontal ligament

In the periodontal ligament (PDL) of normal rat molars, a considerable number of dendritic cells (DCs) are distributed as resident immunocompetent cells. We have hypothesized that the resident type of DCs can alter their morphology and phenotype to adapt to the microenvironment of the PDL. Thus, we have compared the characteristics of DCs in various regions of rat PDL by immunoelectron microscopy and gene expression analysis by means of reverse transcription/polymerase chain reaction. DCs in the periapical region show immature characteristics, i.e., small round profiles and few organelles. In the mesial region, which is the most stable area in the PDL, the density of DCs is the highest. DCs in the furcal region show the characteristics of activated antigen-presenting cells, i.e., CD86(high) expression, electron-dense lysosomes, and cell-to-cell contacts with lymphocytes. When the PDL is bacterially challenged by pulp exposure, the number of CD86+ DCs and contacts with lymphocytes increase in the furcal region. Gene expression analysis for the furcal region has also shown the up-regulation of the major histocompatibility complex class II alpha-chain, CD83, CD86, and the antigen-presenting cell-lectin-like receptor A1. Thus, we have demonstrated heterogeneity in resident DCs. This may be associated with the difference in DCs regarding their state of maturation/activation, which may further reflect microenvironmental differences such as the amount of external antigens.

Reticulohistiocytosis

Reticulohistiocytoses consist of a rare group of diseases caused by CD68+ macrophage proliferation. Several advances have been achieved in relation to the receptors involved in these diseases. This knowledge will clarify the physiopathologic mechanisms of the reticulohistiocytoses and direct better therapeutic approaches for patients.

Alterations in the epidermal-dermal melanin axis and factor XIIIa melanophages in senile lentigo and ageing skin

BACKGROUND

Senile lentigo (SL) is a pigmentation disorder that occurs predominantly on the dorsa of the hands, the forearms and the face; its incidence increases with age. Histological hallmarks of SL lesions are hyperpigmentation of the epidermis and elongation of the epidermal rete ridges. Various factors such as alpha-melanocyte-stimulating hormone, endothelin-1 or stem cell factor are involved in the onset and maintenance of the increased pigmentation. Alterations of the dermal compartment have not yet been analysed in detail in SL.

OBJECTIVES

To study the occurrence and distribution of melanin in the dermis from SL and aged skin, biopsies from 12 subjects were morphologically analysed by light and electron microscopy in comparison with unaffected skin.

METHODS

Punch biopsies of SL and adjacent skin from 12 male or female volunteers aged 52-81 years were prepared for light and electron microscopy and samples were analysed by morphological, morphometric, histochemical and immunohistochemical methods.

RESULTS

The epidermis from SL revealed morphological features such as hyperpigmentation of basal keratinocytes and the formation of elongated rete ridges. S100+ melanocytes in the stratum basale were not markedly increased, indicating that the hyperpigmentation is predominantly due to changes in melanin synthesis, distribution or turnover. Quantification of epidermal cells expressing the proliferation marker Ki67 did not show an increase of this parameter in SL, indicating that at least in the established lesion cell proliferation is not enhanced. We further focused on the dermal compartment and observed granulated cells which were more abundant in SL. Electron microscopic and histochemical analysis revealed that the granulation of these cells is based on melanosomes, mostly present in large melanosomal complexes. Immunohistochemistry using antibodies to CD68 and factor XIIIa (FXIIIa) showed these melanophages to be predominantly FXIIIa+ dermal dendrocytes, which were about six times more abundant than CD68+ macrophages.

CONCLUSIONS

In SL an increased number of melanophages was found compared with unaffected skin from the same subject. These melanophages were identified as FXIIIa+ dermal dendrocytes. Possible functional consequences of the massive melanin uptake by dermal dendrocytes are discussed.

Biology of Langerhans cells and Langerhans cell histiocytosis

Langerhans cells (LC) are epidermal dendritic cells (DC). They play an important role in the initiation of immune responses through antigen uptake, processing, and presentation to T cells. Langerhans cell histiocytosis (LCH) is a rare disease in which accumulation of cells with LC characteristics (LCH cells) occur. LCH lesions are further characterized by the presence of other cell types, such as T cells, multinucleated giant cells (MGC), macrophages (MPhi), eosinophils, stromal cells, and natural killer cells (NK cells). Much has been learned about the pathophysiology of LCH by studying properties of these different cells and their interaction with each other through cytokines/chemokines. In this review we discuss the properties and interactions of the different cells involved in LCH pathophysiology with the hope of better understanding this enigmatic disorder.

Prospective highlights of functional skin proteomics

Although a wide variety of protein profiles have been extensively constructed via proteomic analysis, the comprehensive proteomic profiling of the skin, which is considered to be the largest organ of the human body, is still far from complete. Our efforts to establish the functional skin proteome, a protein database describing the protein networks that underlie biological processes, has set in motion the identification and characterization of proteins expressed in the epidermis and dermis of the BALB/c mice. In this review, we will highlight various cutaneous proteins we have characterized and discuss their biological functions associated with skin distress, immunity, and cancer. This type of research into functional skin proteomics will provide a critical step toward understanding disease and developing successful therapeutic strategies.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Langerhans cells from human oral epithelium are more effective at stimulating allogeneic T cells in vitro than Langerhans cells from skin

This report is focused on the functional capacity of Langerhans cells (LC) in the epithelium of skin and oral mucosa, which both meet different antigenic challenges. The capacity of LC from human oral and skin epithelium to provide co-stimulatory signals to T cells in vitro was compared. LC in a crude suspension of oral epithelial cells had a significantly enhanced T cell co-stimulatory capacity compared to skin epithelial cells. This applied both to cultures with concanavalin A (con-A)-stimulated syngeneic T cells and to a mixed epithelial cell lymphocyte reaction involving allogeneic T cells. The co-stimulatory capacity of oral and skin epithelial cells was reduced by >70% if monoclonal antibodies against HLA-DR, -DP and -DQ were added to the cultures with allogeneic T cells, indicating the involvement of HLA class II expressing LC. Immunohistochemistry revealed that 6% of the epithelial cells were CD1a + LC in sections from both oral and skin epithelium. Interleukin (IL)-8 production was higher in cultures of oral epithelial cells and con-A stimulated T cells than in corresponding cultures with skin epithelial cells as accessory cells. The results suggest that LC in human oral epithelium are more efficient at stimulating T cells than those of skin.

Dermal dendritic cell number correlates with serum autoantibody titers in Brazilian pemphigus foliaceus patients

Pemphigus foliaceus (PF) is an autoimmune bullous disease endemic in Brazil. Since serum IL-12 is increased in patients with PF and Langerhans cells (LC) produce IL-12, we titrated serum autoantibodies by indirect immunofluorescence, and quantified epidermal dendritic cells, known as LC, and dermal dendritic cells (DC). Biopsies of blistering lesions were obtained from 22 patients, 13 of whom were submitted to biopsy of both injured and of apparently healthy skin. The control groups consisted of skin from 8 cadavers and from 12 women submitted to breast plastic surgery. LC and DC were identified with anti-CD1a antibody and quantified by morphometric analysis. LC number in the lesion and in apparently healthy skin from PF patients was similar to that of both control groups. DC number in the injured skin (median=0.94 DC/mm basement membrane) was higher than that of the cadaver group (median=0.13 DC/mm basement membrane). In the 13 patients with biopsies of both injured and apparently healthy skin, LC and DC were present in larger numbers in the lesion. There was a direct correlation between DC number in the lesion of the PF group and serum autoantibody titers. This correlation was not observed for LC number. The increased number of DC in the lesion, as well as its direct correlation with serum autoantibody titers suggest the participation of DC in the pathogenesis of PF. The relationship between increased DC number and IL-12 in PF needs to be clarified.

Hyaluronan-oligosaccharide-induced transcription of metalloproteases

Activated dendritic epidermal Langerhans cells and metastatic tumour cells share many properties. Both cell types can invade the surrounding tissue, enter the lymphatic system and travel to regional lymph nodes. We have recently shown that fragments of the extracellular matrix component hyaluronan, which are typically produced at sites of inflammation, can activate dendritic cells. Upon activation, dendritic cells upregulate expression of matrix metalloproteases (MMPs). These observations prompted us to investigate whether exposure to hyaluronan fragments also induces MMP expression in tumour cells. Here, we report that MMP-9, MMP-13 and urokinase plasminogen activator are upregulated in murine 3LL tumour cells after exposure to mixed-size hyaluronan. Similarly upregulated MMP-9 and MMP-13 expression was observed in primary fibroblasts. By using size-fractionated hyaluronan preparations, we show that the enhanced expression of MMP-9 and MMP-13 is only induced by small hyaluronan (HA) fragments. Although our data suggest that HA-fragment-induced MMP-9 and MMP-13 expression is receptor mediated, they rule out an involvement of the hyaluronan receptors CD44, RHAMM/IHAP and TLR-4. Finally, we show that HA fragment-induced MMP-9 transcription is mediated via NF-κB. Our results suggest that the metastasis-associated HA degradation in tumours might promote invasion by inducing MMP expression.

Association of allergic contact dermatitis with a promoter polymorphism in the IL16 gene

BACKGROUND

There is evidence that IL-16, a cytokine that induces chemotactic responses in CD4(+) T cells, eosinophils, and dendritic cells, plays an important role during different types of cutaneous inflammatory responses, including allergic contact dermatitis (ACD) and atopic dermatitis (AD).

OBJECTIVES

We sought to test for association between a promoter polymorphism in the IL16 gene (T to C transition at position -295) and ACD and AD, respectively.

METHODS

IL16 -295 genotypes were determined in samples from 2 separate case-control studies with white individuals. The first study included healthy individuals (n = 310) and patients with ACD (n = 86). These patients were polysensitized as defined by a contact sensitization to para-substituted aryl compounds and at least one other structurally unrelated allergen. The second study comprised healthy subjects (n = 214) and patients with AD (n = 94).

RESULTS

IL16 -295 genotypes were differently distributed among polysensitized and healthy control subjects (P =.0021). In particular, the IL16 -295*C/C genotype was overrepresented among polysensitized individuals (7.0% vs 1.0% in the control group; odds ratio, 7.68; 95% CI, 1.59-48.12). In contrast, there was no evidence for an association between the IL16 -295 polymorphism and AD.

CONCLUSION

The IL16 -295 promoter polymorphism might influence susceptibility to contact allergy.

Antigens onto bare skin: a 'painless' paradigm shift in vaccine delivery

The skin is an attractive route for delivery of vaccines because it is accessible and contains immunocompetent cells. This opens up the possibility that, in the future, vaccines could be administered in a simple, safe and practical way without requiring the use of needles and syringes. This review focuses on the methods developed to deliver vaccines via the intact skin. Candidate vaccine antigens can be delivered topically using particulate delivery systems and patch formulations containing the antigen with an ADP-ribosylating exotoxin as an adjuvant. The duration and type of elicited immune responses depend on the antigen, the adjuvant and the method of delivery. Already, the first clinical trial of transcutaneous delivery of vaccines has demonstrated the proof of the principle. However, despite these successes, there are several challenges ahead to be addressed before vaccines administered with a patch will be available over the counter.

Antigen presentation to naive CD4 T cells in the lymph node

Although the presentation of peptide-major histocompatibility complex class II (pMHC class II) complexes to CD4 T cells has been studied extensively in vitro, knowledge of this process in vivo is limited. Unlike the in vitro situation, antigen presentation in vivo takes place within a complex microenvironment in which the movements of antigens, antigen-presenting cells (APCs) and T cells are governed by anatomic constraints. Here we review developments in the areas of lymph node architecture, APC subsets and T cell activation that have shed light on how antigen presentation occurs in the lymph nodes.

Allergic skin and systemic reactions in a patient with pure red cell aplasia and anti-erythropoietin antibodies challenged with different epoetins

Recent concern has arisen about the development of neutralizing anti-erythropoietin (EPO) antibodies during the course of treatment with recombinant EPO. The underlying mechanisms are poorly understood. A patient was observed who developed wheals at the sites of subcutaneous injections of epoetin-alpha before the manifestation of pure red cell aplasia (PRCA). Intravenous application of different epoetins evoked skin reactions at the sites of former subcutaneous injections, indicating local persistence of sensitized cells, and eventually a systemic anaphylactoid response. Anti-EPO antibodies crossreactive with epoetin-beta and darbepoetin-alpha were demonstrated in patient serum. PRCA gradually improved after treatment with prednisolone.

Identification and characterization of the low-affinity receptor for immunoglobulin E (FcepsilonRII/CD23) on murine Langerhans cells

CD23 is a low-affinity receptor for immunoglobulin E and expressed on various hemopoietic cells. Although human epidermal cultured Langerhans cells express CD23, the study to identify CD23 on murine Langerhans cells has so far failed. In this study, using highly enriched (> 95%) Langerhans cells from murine epidermis obtained by the panning method, we investigated whether murine Langerhans cells express CD23. As the result of a series of experiments using fluorescence activated cell sorter analysis and the polymerase chain reaction method, it was revealed that CD23 is expressed on cultured Langerhans cells, but not on freshly isolated Langerhans cells. Comparison of the DNA sequence of polymerase chain reaction products of CD23 from cultured Langerhans cells with that from spleen leukocytes demonstrated that there were the same sequences between the two polymerase chain reaction products. The expression of CD23 on cultured Langerhans cells was downregulated when Langerhans cells were cultured with keratinocyte-derived cytokines: interleukin-1alpha, interleukin-18, macrophage colony-stimulating factor, or granulocyte-macrophage colony-stimulating factor. Moreover, it was shown that murine IgE bound to cultured Langerhans cells and this binding was partially inhibited when Langerhans cells were cultured with monoclonal antibody against CD23 (B3B4). Thus this study revealed murine cultured Langerhans cells do express CD23 and the discrepancy from previous reports may be due to the influence of cytokines derived from keratinocytes. Furthermore, the finding that murine cultured Langerhans cells bind IgE through CD23 suggests that CD23 on murine Langerhans cells may be involved in IgE-mediated immune responses.

Catecholamines inhibit the antigen-presenting capability of epidermal Langerhans cells

The sympathetic nervous system modulates immune function at a number of levels. Within the epidermis, APCs (Langerhans cells (LC)) are frequently anatomically associated with peripheral nerves. Furthermore, some neuropeptides have been shown to regulate LC Ag-presenting function. We explored the expression of adrenergic receptors (AR) in murine LC and assessed their functional role on Ag presentation and modulation of cutaneous immune responses. Both purified LC and the LC-like cell lines XS52-4D and XS106 expressed mRNA for the ARs alpha(1A) and beta(2). XS106 cells and purified LC also expressed beta(1)-AR mRNA. Treatment of murine epidermal cell preparations with epinephrine (EPI) or norepinephrine inhibited Ag presentation in vitro. Furthermore, pretreatment of epidermal cells with EPI or norepinephrine in vitro suppressed the ability of these cells to present Ag for elicitation of delayed-type hypersensitivity in previously immunized mice. This effect was blocked by use of the beta(2)-adrenergic antagonist ICI 118,551 but not by the alpha-antagonist phentolamine. Local intradermal injection of EPI inhibited the induction of contact hypersensitivity to epicutaneously administered haptens. Surprisingly, injection of EPI at a distant site also suppressed induction of contact hypersensitivity. Thus, catecholamines may have both local and systemic effects. We conclude that specific ARs are expressed on LC and that signaling through these receptors can decrease epidermal immune reactions.

Langerhans cells and T cells in oral graft versus host disease and oral lichen planus

Chronic graft versus host disease (cGVHD) of the oral mucosa, following allogeneic stem cell transplantation, and oral lichen planus (OLP) are both mucosal diseases where the immune system is involved in the pathogenesis. Although the aetiology of the two conditions is different, they present with a similar clinical appearance. This study compares the two diseases regarding the distribution of cells, which are expressing cell surface markers of interest for inflammatory responses. Monoclonal antibodies (MoAbs) were used in standard immunohistochemical procedures. CD1a+, CD80+ and CD86+ cells in the epithelium of OLP- and cGVHD lesions had the dendritic morphology of Langerhans cells (LC). Higher frequencies of CD1a+ LC as well as CD25+ cells were observed in the OLP epithelium than in the cGVHD epithelium. The OLP lesions showed higher frequencies of subepithelial cells expressing CD1a, CD86, CD4, CD8 and CD25 than the cGVHD lesions. Notably there was a significantly higher frequency of CD25+ cells in the epithelium and the connective tissue of OLP than in cGVHD. These cells might represent regulatory T cells. In conclusion, cGVHD and OLP show marked differences at the cellular level despite similar clinical appearance. Hence, the findings indicate differences in the regulation of the inflammatory response between the two conditions.

Peripheral blood granulocyte activity following contact sensitization of rats with dinitrochlorobenzene

Contact hypersensitivity (CHS) reaction is a classic example of a cell-mediated reaction. As the afferent phase of the reaction includes inflammation, CHS is a suitable model for investigating non-specific immunity. Some aspects of granulocyte activity in the afferent phase of experimentally induced CHS to dinitrochlorobenzene (DNCB) in two genetically different rat strains, AO and DA were examined in this study. A shift in the ratio of granulocytes to lymphocytes in favour of granulocytes and an increase in granulocyte survival were noted in DA rats. Granulocytes from both strains demonstrated increased levels of NBT reduction and an increase in their adhesion to plastic. Decreased granulocyte adhesion in the presence of monoclonal antibodies to beta2 integrins (anti-CD11b/c and anti-CD18) points to the contribution of these molecules to granulocyte adhesiveness during the sensitization phase of CHS. Stimulation of adhesion in the presence of anti-CD11a antibody, points to a differential modulation of adhesion molecule activity during the afferent phase of CHS. Changes in functional activity of granulocytes demonstrated in this study might contribute to the development of CHS in rats.

Immunization onto bare skin with heat-labile enterotoxin of Escherichia coli enhances immune responses to coadministered protein and peptide antigens and protects mice against lethal toxin challenge

In this study, the potential of the bare skin as a non-invasive route for vaccination was examined. Following application of heat-labile enterotoxin (LT) of Escherichia coli onto bare skin of BALB/c mice, strong serum anti-LT antibody responses were observed, and mucosal immunoglobulin A (IgA) and IgG antibodies were measured in vagina washes. In addition, LT enhanced the serum and mucosal antibody and proliferative T-cell responses to the model protein antigen beta-galactosidase (beta-gal) when coadministered onto bare skin, highlighting its potential to exert an adjuvant effect. When a peptide representing a T-helper epitope (aa 307-319) from the haemagglutinin of influenza virus was applied onto bare skin with LT or cholera toxin (CT), it primed effectively peptide- and virus-specific T cells, as measured in vitro by the interleukin-2 (IL-2) secretion assay. LT was shown to be as immunogenic as CT. Binding activity to GM1 gangliosides was essential for effective induction of anti-CT serum and mucosal antibody responses. Finally, mice immunized onto bare skin with LT were protected against intraperitoneal challenge with a lethal dose of the homologous toxin. These findings give further support to a growing body of evidence on the potential of skin as a non-invasive route for vaccine delivery. This immunization strategy might be advantageous for vaccination programmes in Third World countries, because administration by this route is simple, painless and economical.

Therapeutic application of T cell receptor mimic peptides or cDNA in the treatment of T cell-mediated skin diseases

An 8-amino acid peptide encoding a sequence of the transmembrane region of the T cell receptor alpha chain (TCR-alpha) was shown to inhibit T cell function by preventing functional assembly of the T cell receptor (mimic peptide). To avoid systemic immunosuppression by peptide application in vivo, we used a topical application of the peptide. In the system of murine contact sensitivity, topical application of the peptide inhibited the elicitation of contact sensitivity following application of a contact allergen in sensitized animals. Alternatively, when naked DNA encoding the peptide sequence was injected into skin before application of a contact allergen to sensitized animals, local immunosuppression was also observed. To investigate the effects of this peptide in humans, patients with psoriasis, atopic eczema, lichen planus, or contact dermatitis were treated topically with mimic peptide or control peptide. All patients except for one reported a marked improvement or cure of their skin disease following application of the TCR-alpha peptide, but not controls. These data indicate that TCR-alpha peptide or cDNA treatment might be a proper treatment for human T cell-mediated dermatoses substituting for corticosteroids.

Cytokines and chemokines in the initiation and regulation of epidermal Langerhans cell mobilization

Langerhans cells (LC) are members of the wider family of dendritic cells. LC reside in the epidermis where they serve as sentinels of the immune system, their responsibilities being to sample the external environment for changes and challenges and to deliver information (antigen) to responsive T lymphocytes within skin draining lymph nodes. The ability of LC to migrate from the epidermis to regional lymph nodes is therefore of pivotal importance to the induction of cutaneous immune responses. The journey that LC have to make from the skin has a number of requirements. Initially it is necessary that LC disassociate themselves from surrounding keratinocytes and are liberated from other influences that encourage their retention in the epidermis. Subsequently, migrating LC must successfully traverse the basement membrane of the dermal-epidermal junction and make their way, via afferent lymphatics, to draining lymph nodes. Effective entry into lymph nodes is necessary, as is correct positioning of cells within the paracortex. There is increasing evidence that both cytokines and chemokines, and their interaction with appropriate receptors expressed by LC, orchestrate the mobilization and movement of these cells. We here consider the parts played by these molecules, and how collectively they induce and direct LC migration.

Factor XIIIa positive dendritic cells are a major accessory cell population in the elicitation phase of DNCB-induced contact hypersensitivity

The phenotypes and distribution of accessory cells in the ear skin of lambs during the elicitation phase of dinitrochlorobenzene (DNCB)-induced contact hypersensitivity (CHS) were examined using indirect immunoperoxidase histochemistry (ABC method), and a panel of antibodies. Thirty lambs, between 21 and 26 weeks of age, were divided into groups of 10. The shaved right ear of one group was treated with DNCB. Two weeks later this group was challenged with DNCB. One group was treated with the vehicle alone and the remaining group was left untreated. The lambs were slaughtered 48 h after challenge, and tissue specimens were collected from the ears of the three groups. Factor XIIIa+ (FXIIIa+) cells were prominent in the superficial dermis and showed predominantly a perivascular and subepidermal distribution. The other markers were less prominent, and whereas CD1+ cells and CD68+ cells showed a reaction pattern similar to the FXIIIa+ cells, CD14+ cells were found scattered predominantly in the deep dermis. There appeared to be an increase in FXIIIa+ cells, CD1+ cells, and CD68+ cells in the dermis of the DNCB-treated lambs 48 h after challenge. Only CD1+ cells were detected in epidermis of normal controls, and these cells appeared to be decreased in number in the two treated groups. Computer-assisted morphometric analysis was used to estimate the relative presence of the accessory cell subpopulations in the superficial and deep dermis and the entire dermis. A statistical analysis of the relative area of immunostaining showed a significantly increased presence of FXIIIa+ cells and CD68+ cells in the dermis of the DNCB-treated lambs 48 h after challenge. Interestingly, FXIIIa+ cells and CD68+ cells were also significantly increased in the vehicle treated group compared with untreated controls. We found no significant difference in the presence of CD1+ cells or CD14+ cells in the DNCB treated group compared with the controls. The study showed that FXIIIa+ DDC are the major accessory cell population in normal ear skin of lambs and the major responsive population during the elicitation phase of CHS. The lack of response in the CD1+ cell population suggests a less prominent role for the LC-related DC in the skin during the elicitation phase.

Inhibition by dexamethasone of Langerhans cell migration: influence of epidermal cytokine signals

The influence of dexamethasone (DEX), a synthetic glucocorticoid, on the induction in mice of Langerhans cell (LC) migration has been investigated. Systemic treatment of mice with DEX was found to inhibit significantly the ability of a topically applied contact allergen (oxazolone) to induce the migration of LC from the epidermis and their subsequent accumulation as dendritic cells (DC) in draining lymph nodes. The stimulation of LC migration during skin sensitization is dependent upon signals provided by the epidermal cytokines tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta). It was found that treatment with DEX was unable to inhibit either LC migration or DC accumulation induced by the intradermal injection of TNF-alpha. In contrast, LC migration provoked by similar exposure of mice to IL-1beta (the action of which is dependent upon the de novo synthesis of TNF-alpha) was inhibited by DEX as was the arrival of DC in draining lymph nodes induced by this cytokine. Taken together, the data reported here indicate that DEX is able to inhibit very markedly the stimulation of LC migration during skin sensitization and it is proposed that such inhibition may represent an important aspect of the immunosuppressive properties of glucocorticoids and of their proven utility in the treatment of cutaneous inflammatory disorders. The results also indicate that DEX does not inhibit LC migration secondary to direct effects on cell motility. The proposal is that impaired LC migration results from the regulation by DEX of the de novo synthesis and/or release of TNF-alpha, an inducible epidermal cytokine that provides one important signal for LC to traffic from the skin.

Colonization of in vitro-formed cervical human papillomavirus- associated (pre)neoplastic lesions with dendritic cells: role of granulocyte/macrophage colony-stimulating factor

The purpose of this study was to investigate the ability of CD1a+ Langerhans/dendritic cells (LCs/DCs) to infiltrate human papillomavirus (HPV)-associated (pre)neoplastic lesions of the uterine cervix. Migration of LCs/DCs in the presence of keratinocytes derived from normal cervix and HPV-transformed cell lines was evaluated in Boyden chambers and in organotypic cultures and correlated with granulocyte/macrophage colony-stimulating factor (GM-CSF) production by the cells, as determined by ELISA. Conditioned media of HPV-transformed keratinocytes contained lower amounts of GM-CSF and induced a decreased motile response of LCs/DCs in the Boyden chamber assay compared with those of normal cervical keratinocytes. The migration of LCs/DCs in the presence of conditioned media from normal keratinocytes could be blocked by an anti-GM-CSF antibody, and the migration of LCs/DCs in the presence of conditioned media from HPV-transformed keratinocytes could be increased by supplementing the media with recombinant GM-CSF. GM-CSF was also a potent factor in enhancing the colonization of LCs/DCs into organotypic cultures of HPV-transformed keratinocytes, as the infiltration of LCs/DCs in the in vitro-formed (pre)neoplastic epithelium was minimal under basal conditions and dramatically increased after the addition of GM-CSF to the cultures. These results suggest that GM-CSF could play an important role in the recruitment of LCs/DCs into the HPV-transformed (pre)neoplastic cervical epithelium and be useful as a new immunotherapeutic approach for cervical (pre)cancers.