Effects of topical corticosteroid therapy on Langerhans cell antigen presenting function in human skin

Further Evidence of Allergic Contact Dermatitis Caused by 2,2'-Methylenebis(6-tert-Butyl-4-Methylphenol) Monoacrylate, a New Sensitizer in the Dexcom G6 Glucose Sensor

BACKGROUND

Since the spring of 2020, we have seen several patients experiencing severe allergic contact dermatitis (ACD) from the Dexcom G6 glucose sensor after the composition of the sensor's adhesive patch had been changed. We have previously reported the finding of a new sensitizer, 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate, in the Dexcom G6 adhesive patch. Three patients with ACD from Dexcom G6 tested positive to this sensitizer. They were also allergic to isobornyl acrylate, a sensitizer present both in Dexcom G6 and in other medical devices previously used by these patients.

OBJECTIVE

The aim of the study was to report the first 4 cases sensitized to 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate without a simultaneous allergy to isobornyl acrylate.

METHODS

The cases were patch tested their own materials, a medical device series, and 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate in several concentrations.

RESULTS

All 4 cases tested positive to 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate at either 1.0% or 1.5% in petrolatum, whereas 20 controls tested negative to both concentrations.

CONCLUSIONS

The cases reported here provide further evidence of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate as a relevant culprit sensitizer in patients with ACD from Dexcom G6. However, the initially used patch test concentration (0.3%) did not suffice to elicit positive reactions in these cases, which is why patch testing at 1.5% is recommended.

Transcriptomes from German shepherd dogs reveal differences in immune activity between atopic dermatitis affected and control skin

Canine atopic dermatitis (CAD) is an inflammatory and pruritic allergic skin disease with both genetic and environmental risk factors described. We performed mRNA sequencing of non-lesional axillary skin biopsies from nine German shepherd dogs. Obtained RNA sequences were mapped to the dog genome (CanFam3.1) and a high-quality skin transcriptome was generated with 23,510 expressed gene transcripts. Differentially expressed genes (DEGs) were defined by comparing three controls to five treated CAD cases. Using a leave-one-out analysis, we identified seven DEGs: five known to encode proteins with functions related to an activated immune system (CD209, CLEC4G, LOC102156842 (lipopolysaccharide-binding protein-like), LOC480601 (regakine-1-like), LOC479668 (haptoglobin-like)), one (OBP) encoding an odorant-binding protein potentially connected to rhinitis, and the last (LOC607095) encoding a novel long non-coding RNA. Furthermore, high mRNA expression of inflammatory genes was found in axillary skin from an untreated mild CAD case compared with healthy skin. In conclusion, we define genes with different expression patterns in CAD case skin helping us understand post-treatment atopic skin. Further studies in larger sample sets are warranted to confirm and to transfer these results into clinical practice.

The role of Langerhans cells in pathologies of the skin

Langerhans cells (LCs) are epidermal immune cells of myeloid origin. Although these cells were primarily thought to play a defensive role in the skin, evidence now indicates a diverse range of LC-mediated effects including the relay of viral antigens in herpes simplex infection, recruitment of eosinophils in atopic dermatitis and promotion of a Th17 response in Candida infection. LCs may have a protective or suppressive function in pathologies of the skin, with differing functions being driven by the skin milieu. Understanding LC function will help guide the development of interventions that modulate these cells for therapeutic benefit.

Differential Induction of IL-12 p40 and IL-10 mRNA in Human Langerhans' Cells and Keratinocytes by in Vivo Occlusion, Vehicle, and All-TRANS Retinoic Acid

Background:

Hydration and pharmacologic manipulation of the skin may have immunomodulatory effects. For instance, retinoic acid (RA) in vivo upregulates antigen-presenting cell (APC) activity of Langerhans' cells (LC).

Objective:

Our study was to determine whether RA increases LC APC activity via alteration of the potent immunoregulatory and reciprocally acting cytokines, IL-12 and IL-10.

Methods:

0.1% RA and vehicle solvent only (V) as a control were applied under occlusion on the skin of normal volunteers. Freshly selected CD1a+ LC and keratinocytes from keratome were subject to semiquantitative determination of IL-12 p40 and IL-10 mRNA levels. IL-12 p40 protein was measured by radioimmunoassay.

Results:

Occlusion alone and open vehicle alone did not induce LC immunoregulatory cytokines; LCs demonstrated significant induction of IL-12 p40 mRNA, when the vehicle was occluded for 48 hours and, to a lesser extent, IL-10 as well. IL-12 p40 mRNA could be further induced by RA-LC at the 20-hour time point; however, IL-10 mRNA was induced at the 48-hour time point. Neither occlusion nor RA significantly induced IL-12 p40 or IL-10 mRNA in CD1a keratinocytes at any time points.

Conclusion:

A tight reciprocal regulation of IL-10 and IL-12 is present in LCs and is consistent with the initial, but self-limited, inflammatory effect of occlusion and topical retinoids.

The immune microenvironment in cutaneous leishmaniasis

BACKGROUND

Cutaneous leishmaniasis is an infection that has spread to non-endemic regions, stimulating recent interest for the enhanced understanding of this disease. Downregulation of the CD1a receptor on Langerhans cells has been described in various cutaneous infections.

OBJECTIVE

In this study, the immune response across different Ridley patterns and parasitic indices is outlined in a case series of cutaneous leishmaniasis.

METHODS

Skin punch biopsies from the interface of normal and lesional cutaneous leishmaniasis were collected from 33 patients with molecularly confirmed Leishmania tropica or L. major infection. Ridley patterns (2-5) were assessed for various clinicopathological features including age, gender, disease duration, parasitic index and constituents of the inflammatory infiltrate. CD1a, CD68, CD3, CD4, CD8, CD20 and CD138 stains were performed on normal skin tissue, cutaneous leishmaniasis biopsies and cytospin/cell block cytology preparations of cultured leishmania promastigotes. CD1a was quantified per mm2 in the epidermis and dermis. The remaining stains were graded according to a 4-tiered grading system [0 (0-4%); 1 (5-24%); 2 (25-49%); 3 (50-74%) and 4 (75-100%).

RESULTS

Total CD1a expression significantly decreased (14-fold) from parasitic indices (0-2) to (5-6); (ρ < 0.001). CD1a expression in the epidermis was at least 5-fold lower than normal skin (58 vs. 400 cells/mm2), inversely correlating with the parasitic index. There was an increase in dermal CD1a Langerhans cells (33 vs. 0 cells/mm² in the dermis). CD1a and CD68 staining of amastigotes was strong and diffuse, whereas promastigotes were negative. The major inflammatory infiltrate, in all Ridley patterns, consisted of macrophages and double-negative CD3(+) CD4(-) CD8(-) T lymphocytes. The double-negative CD3 T cells formed a ring around the parasitic laden macrophages. Apart from CD1a, there was no significant difference in inflammatory markers between the various Ridley patterns and parasitic indices. Disease duration did not correlate with Ridley pattern.

CONCLUSION

The significant decrease in CD1a expression is postulated by two mechanisms; either via direct CD1a receptor uptake by leishmania amastigotes and/or negative feedback inhibition of CD1a Langerhans cells by double-negative CD3 T-regulatory cells. Modulation of the immune microenvironment in cutaneous leishmaniasis represents a potential therapeutic and prophylactic target.

Stressful presentations: mild cold stress in laboratory mice influences phenotype of dendritic cells in naïve and tumor-bearing mice

The ability of dendritic cells (DCs) to stimulate and regulate T cells is critical to effective anti-tumor immunity. Therefore, it is important to fully recognize any inherent factors which may influence DC function under experimental conditions, especially in laboratory mice since they are used so heavily to model immune responses. The goals of this report are to 1) briefly summarize previous work revealing how DCs respond to various forms of physiological stress and 2) to present new data highlighting the potential for chronic mild cold stress inherent to mice housed at the required standard ambient temperatures to influence baseline DCs properties in naïve and tumor-bearing mice. As recent data from our group shows that CD8⁺ T cell function is significantly altered by chronic mild cold stress and since DC function is crucial for CD8⁺ T cell activation, we wondered whether housing temperature may also be influencing DC function. Here we report that there are several significant phenotypical and functional differences among DC subsets in naïve and tumor-bearing mice housed at either standard housing temperature or at a thermoneutral ambient temperature, which significantly reduces the extent of cold stress. The new data presented here strongly suggests that, by itself, the housing temperature of mice can affect fundamental properties and functions of DCs. Therefore differences in basal levels of stress due to housing should be taken into consideration when interpreting experiments designed to evaluate the impact of additional variables, including other stressors on DC function.

Photocarcinogenicity of selected topically applied dermatological drugs: calcineurin inhibitors, corticosteroids, and vitamin D analogs

Topical therapies constitute the mainstay of dermatological treatments for skin disorders, such as atopic dermatitis, contact dermatitis, psoriasis, or acne. Since some of these diseases are often chronic, treatment duration may last for years and may even last the patient's entire lifetime. Obviously, such long-term therapy may raise safety concerns, which also include the potential photocarcinogenic effect. Most patients are exposed to ultraviolet radiation (UVR) during leisure, work, vacations, or in tanning beds. Additionally, the patients may receive UVR via UVB phototherapy or psoralens plus UVA radiation (PUVA). The use of immunosuppressant's, such as corticosteroids and calcineurin inhibitors, has markedly increased. Patients with skin diseases have benefited from both systemic and topical treatment of both new and established drugs. The issue of a black box warning by the US Food and Drug Administration has increased concerns about photocarcinogenesis, which raises the question: "Are these drugs safe?" This review focuses on the mechanism of action and photocarcinogenic potential of commonly used topical treatments, such as corticosteroids, calcineurin inhibitors, and vitamin D analogs.

Neuroendocrine regulation of skin dendritic cells

It has long been postulated that stress can affect certain skin conditions, and there is increasing experimental evidence that the neuroendocrine system can directly participate in cutaneous inflammation. Neurohormones, such as glucocorticoids and catecholamines, can reach the skin through the bloodstream after activation of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, respectively. Multiple neuropeptides, among them calcitonin gene-related peptide, alpha-melanocyte stimulating hormone, pituitary adenylate cyclase-activating peptide, substance P, vasoactive intestinal peptide, and norepinephrine, may be released by cutaneous nerves or resident and infiltrating cells within the skin. Systemic neuromediators and cutaneous nerves can influence a number of target cells within the skin, among them Langerhans cells. Most of the experimental evidence to date indicates a suppressive effect of the neurohormones and neuropeptides on Langerhans cell function and cutaneous inflammation, but it has become evident lately that the timing of exposure to a stimulus is critical to the outcome of the immune response. Thus, administration of a stress hormone or exposure to a stressor before the dendritic cell (DC) encounters an antigen (Ag) may diminish the immune response toward that Ag, while a stressor may enhance immune function when acting on a maturing DC or before reexposure to the Ag. The neuroendocrine regulation of skin DCs is a complex system allowing for a quick adaptation to various stressors. Such a system, originally evolved to defend the organism against invading pathogens and maintain homeostasis, may under certain conditions become unbalanced and ultimately exacerbate cutaneous inflammation.

Review of the potential photo-cocarcinogenicity of topical calcineurin inhibitors. Position statement of the European Dermatology Forum

Topical Calcineurin Inhibitors (TCIs) used for the treatment of atopic eczema modify the immune regulatory function of the skin and may have the potential to enhance immunosuppressive ultraviolet (UV) effects. Current recommendations on UV protection in eczema patients treated with PCIs are inconsistent and have given rise to uncertainty and anxiety in patients. Therefore, the European Dermatology Forum (EDF) developed a position statement which reviews critically the available data with regard to the problem, especially analysing and commenting the limitations of rodent models for the human situation. There is no conclusive evidence from rodent trials to indicate that long-term application of TCIs is photococarcinogenic. There is a need for further studies to investigate the validity of mouse models as well as long-term cohort studies in patients using TCIs. Available data suggest that long-term application of TCIs is safe, that there is no evidence of increased skin cancer risk and that it is ethical to treat patients with TCIs when indicated.

Inflammatory cell numbers and cytokine expression in atopic dermatitis after topical pimecrolimus treatment

BACKGROUND

In several clinical trials the topical application of pimecrolimus was shown to be effective in the treatment of atopic dermatitis (AD). By targeting calcineurin-dependent signaling pathways, pimecrolimus controls cytokine gene expression. The purpose of this study was to investigate the effect of pimecrolimus on the inflammatory infiltrate and cytokine expression pattern in AD upon topical therapy.

METHODS

From 10 patients with acute AD, skin biopsies as well as immunophenotype and cytokine production of peripheral blood mononuclear cells (PBMC) were examined before and 3 weeks after therapy.

RESULTS

The clinical improvement was associated with a marked regression of histopathological features. In particular, the density of the inflammatory infiltrate mostly containing lymphocytes and eosinophils declined. By double immunofluorescent staining, a reduced expression of the T helper (Th) 2 cytokines interleukin (IL)-5, IL-10, and IL-13 in both CD4+ and CD8+ T cells was demonstrated after therapy. Pimecrolimus therapy was also associated with a reduced expression of the Th1 cytokine interferon (IFN)-gamma. Interestingly, the numbers of epidermal CD1a+ dendritic cells increased following treatment. In the peripheral blood, a decrease of lymphocytes and eosinophils was noticed, but the distribution of lymphocyte subpopulations and their capacity of cytokine production did not change.

CONCLUSIONS

Topical pimecrolimus exhibits anti-inflammatory effects in AD by reducing the inflammatory cell infiltrate and cytokine expression in the dermis.

Selective Persistence of Dermal CD8+ T Cells in Lesional Plaque Psoriasis after Clobetasol‐17 Propionate Treatment

In psoriasis, T-cell infiltration and epidermal hyperproliferation are key phenomena which are closely related. Our aim was to investigate the dynamics among T-cell subsets in relation to epidermal proliferation and clinical severity in psoriasis during treatment with an ultra-potent corticosteroid. Seven psoriasis patients were treated twice daily for 14 days with clobetasol-17 propionate ointment. Punch biopsies were taken at day 0, 3, 7 and 14. Epidermal proliferation marker Ki-67 and CD4+, CD8+, CD45RO+, CD2+ T cells were quantified by immunohistochemical techniques and image analysis. The clinical score declined significantly (60%; p<0.01) and a 47% reduction of Ki-67+ nuclei was observed after only 3 days (p<0.01). In the epidermis all investigated T-cell subsets were significantly reduced at day 14 (p<0.05). In the dermis, treatment resulted in a significant decrease of CD4+, CD45RO+ and CD2+ T cells, but dermal CD8+ T cells persisted. In psoriasis, reduction of clinical severity and epidermal proliferation during the early phase of topical corticosteroid therapy cannot primarily be the result of decreased T-cell subsets. Furthermore, selective persistence of dermal CD8+ T cells was observed, which might be associated with disease relapse.

A quantitative study of epidermal Langerhans cells in cutaneous leishmaniasis caused by Leishmania tropica

OBJECTIVE

The purpose of this study was to characterize the number and distribution of epidermal Langerhans cells in different clinical forms of dry-type cutaneous leishmaniasis (CL).

METHODS

Sixteen cases of dry-type cutaneous leishmaniasis caused by Leishmania tropica were studied. These cases were classified clinically as five cases of acute leishmaniasis with indurated papules, nodules and plaques with central crust formation and duration < 2 years, six cases of lupoid leishmaniasis with characteristic papules around previous scars of cutaneous leishmaniasis with duration > 2 years, and five cases of chronic nonlupoid type with nonhealing lesions of duration > 2 years. Paraffin-embedded blocks were stained with hematoxylin and eosin (H&E) and stained immunohistochemically for CD1a.

RESULTS

The number of Langerhans cells per millimeter length of epidermis was increased in acute cases compared to chronic and lupoid cases.

CONCLUSIONS

Lesions of acute leishmaniasis contain the greatest amounts of antigen for presentation, so Langerhans cells increase in number and in trafficking to present antigens derived from Leishman bodies to the cellular immune system. In chronic leishmaniasis, the Langerhans cell population is reduced, perhaps because of exhaustion of the source of Langerhans cells, or because of reduced response to modified antigen.

Measurement of cytokine expression and Langerhans cell migration in human skin following suction blister formation

Contact allergen-induced migration of epidermal Langerhans cells (LCs) to draining lymph nodes is dependent upon receipt by LCs of at least two cytokine signals provided by tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1beta. It has been reported previously that intradermal injection of healthy human volunteers with homologous TNF-alpha or IL-1beta each induces a significant reduction in LC frequency, as measured in epidermal sheets prepared from 6-mm punch biopsies. In the current experiments, we have compared the frequency of LCs in punch biopsies with those obtained concurrently in epidermal sheets from the roofs of suction blisters isolated from the sun-protected buttock skin of healthy adult volunteers. There was a significant, approximately 30%, reduction in CD1a(+) LC numbers in suction blister roofs compared with punch biopsies. Injection of homologous recombinant IL-1beta, a stimulus that provokes measurable epidermal LC mobilization in punch biopsy sites, failed to provoke further LC migration in suction blister sites. These data suggest that the mechanical trauma to the skin caused by the creation of suction blisters provokes the degree of cutaneous inflammation necessary for LC mobilization. The responsive cells (only a proportion of resident LCs, approximately 30%) have already migrated, thus addition of an exogenous cytokine signal (IL-1beta) is without further effect. It is not possible therefore to measure the regulation of LC mobilization by exogenous cytokines in suction blister roofs. However, this technique provides an opportunity to profile induced changes in the cutaneous cytokine environment, with cytokine expression measured by a multiple cytokine array system. Using this technique, intradermal injection of IL-1beta was found to cause a marked upregulation of proinflammatory cytokines including TNF-alpha, IL-6, IL-8, monocyte chemotactic protein-1 (MCP-1) and the anti-inflammatory cytokine IL-10 in fluid from suction blisters raised at the site of injection. In conclusion, the suction blister technique appears to be a powerful tool for measurement of induced changes in cutaneous cytokines.

Pimecrolimus does not affect Langerhans cells in murine epidermis

BACKGROUND

Langerhans cells (LCs) function as specialized antigen-presenting cells in the epidermis, and therefore play a critical role in cutaneous immunological reactions. Topical treatment with corticosteroids is associated with a decrease in epidermal LC number and antigen-presenting capacity in laboratory animals and humans.

OBJECTIVES

To examine whether pimecrolimus, a nonsteroidal inflammatory cytokine inhibitor recently introduced for the topical treatment of atopic dermatitis, differs from corticosteroids in effects on LCs.

METHODS

Groups of BALB/c mice were treated twice daily on one to five consecutive days on the inner surface of the right ear with 10 micro L of ethanolic solutions of the test compounds at their clinically used concentrations (1% pimecrolimus, 0.1% betamethasone-17-valerate, 1% hydrocortisone and 0.05% clobetasol propionate) or with the vehicle (controls) alone. At selected time points after the treatment epidermal sheets were prepared and examined histomorphometrically for LCs immunolabelled with antibodies to major histocompatibility complex (MHC) class II and DEC 205, and adenosine diphosphatase staining.

RESULTS

No changes in number or morphology of LCs were observed in epidermal sheets of mice treated for 5 days with pimecrolimus. In contrast, an almost complete depletion of LCs was observed in skin samples treated with hydrocortisone, betamethasone or clobetasol. Even a single-day treatment schedule with hydrocortisone, betamethasone or clobetasol caused a significant reduction in MHC class II+ LCs, by 31%, 62% and 87%, respectively.

CONCLUSIONS

It is therefore unlikely that topically applied pimecrolimus affects epidermal LCs, in contrast to corticosteroids.

Influence of immunosuppressive drugs on dendritic cells

Immunosuppressive drugs used to control allograft rejection and in efforts to promote transplant tolerance are well recognized for their abilities to inhibit lymphocyte activation and proliferation. In recent years, evidence has accumulated that these diversely acting agents (anti-proliferative drugs, calcineurin inhibitors, rapamycin, deoxyspergualin and glucocorticoids) also affect the development and functional immunobiology of dendritic cells, in vitro and in vivo. Here we review the influence of immunosuppressive drugs on the differentiation and function of these important antigen-presenting cells. We also consider how these effects influence immune reactivity and tolerance induction, implications for furthermore understanding of dendritic cell biology and prospects for improving the outcome of organ transplantation and therapy of other immune-mediated disorders by impacting dendritic cell function.

Functional modulation of dendritic cells to suppress adaptive immune responses

In recent years, dendritic cells (DCs) have entered the center court of immune regulation. Dependent on their ontogeny, state of differentiation, and maturation and thereby a variable expression of membrane-bound and soluble molecules, DCs can induce immunostimulatory as well as immunoregulatory responses. This dual function has made them potential targets in vaccine development in cancer and infections as well as for the prevention and treatment of allograft rejection and autoimmune diseases. The present review is focused on the effect of immune-modulatory factors, such as cytokines and immunosuppressive drugs, and on the survival, differentiation, migration, and maturation of DC human subsets. A better understanding of DC immunobiology may lead to the development of specific therapies to prevent or dampen immune responses.

Corticosteroids prevent generation of CD34+-derived dermal dendritic cells but do not inhibit Langerhans cell development

Corticosteroids (CS) have been shown to exert strong inhibitory effects on dendritic cell (DC) differentiation and function. Those studies were mostly performed with monocyte-derived DC, which represents only one subpopulation from the wide variety of DC types. In the present study the effects of the CS dexamethasone and prednisolone were investigated on the differentiation of CD34(+) hemopoietic progenitor cells into 1) Langerhans cells (LC), which differentiate directly into CD1a(+) DC; and 2) dermal/interstitial DC, which differentiate via a CD14(+)CD1a(-) phenotype into CD14(-)CD1a(+) DC. CS present during the entire 11-day culture period, resulting in fully differentiated CD1a(+) DC, increased the percentage of langerin(+) DC within the CD1a(+) population. In line with these data, CS treatment during the first 6 days of differentiation reduced the development of CD14(+) dermal DC precursors and thereby seemed to support the generation of CD1a(+) LC precursors. Addition of CS from day 6 onward specifically blocked the development of CD1a(+) dermal DC by both inhibition of spontaneous and IL-4-induced differentiation of CD14(+) DC precursors into CD1a(+) DC as well as induction of apoptosis in CD14(+) DC precursors. Apoptosis was not found in CD14(+) macrophage precursors derived from the same CD34(+) progenitors. The development and function of LC were not affected by CS, as demonstrated by a normal T cell stimulatory capacity and IL-12 production. These data demonstrate that CS interfere with the normal development of DC from CD34(+) progenitors by specific induction of apoptosis in precursors of dermal/interstitial DC. In view of the different functional capacities of dermal/interstitial DC and Langerhans cells, this might affect the overall cellular immune response.

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.

Calcipotriol inhibits the proliferation of hyperproliferative CD29 positive keratinocytes in psoriatic epidermis in the absence of an effect on the function and number of antigen-presenting cells

The aim of this study was to elucidate some of the possible mechanisms of action of the vitamin D analogue calcipotriol in vivo. Calcipotriol is finding increasing use in the treatment of psoriasis, but the primary target cell in vivo has not yet been identified. We treated psoriatic patients and healthy volunteers with calcipotriol and placebo ointment for 4 and 7 days, and obtained epidermal cell suspensions from treated areas. Epidermal cells were cocultured with autologous T cells, isolated from peripheral blood, in the absence or the presence of a classical antigen or a superantigen. In both psoriatic and normal skin, calcipotriol treatment did not alter the capacity of epidermal antigen-presenting cells to stimulate the proliferation of autologous T cells, either in the absence or in the presence of exogenous antigen. Epidermal cell suspensions were analysed further by staining for infiltrating leucocytes (CD45+) and Langerhans cells (CD1a+). Flow cytometric analysis showed that calcipotriol did not alter the number of CD45+ cells or Langerhans cells in psoriatic skin. These results indicate that calcipotriol does not alter either the number of the function of epidermal antigen-presenting cells in psoriatic epidermis. In contrast, we found that calcipotriol significantly inhibited the proliferation of epidermal cells isolated from psoriatic skin after in vivo treatment, as determined by propidium iodide staining and flow cytometry. More specifically, we stained for CD29+ keratinocytes and found an even more significant reduction in proliferative capacity. This cell type contains the population of hyperproliferative keratinocytes in psoriatic epidermis. In conclusion, calcipotriol seems to act via an inhibitory effect on hyperproliferative basal keratinocytes of psoriatic epidermis, rather than via an effect on infiltrating leucocytes, including antigen-presenting cells.

Benefits and risks of intralesional corticosteroid injection in the treatment of dermatological diseases

Intralesional corticosteroid (CS) injections have been used to treat a variety of dermatological and non-dermatological diseases with variable results. The purpose of the injection is to attain a high concentration of the drug at the diseased site, with minimal systemic absorption. Several CS preparations are available for intralesional injection, although triamcinolone derivatives have gained the widest usage in dermatology. The dose and the interval between injections depend on the type, size and severity of the lesion as well as the response to the previous injections. The most critical issue in the efficacy and also in the development of complications of the injections, is the method of injection. Several local and systemic side-effects have been reported following intralesional injections, but most of them are rare or acceptable. Thus intralesional CS injection is an integral part of the clinical practice of dermatology. Since their introduction in 1951, intralesional CS injections have become an integral part of clinical practice in dermatology. They are used alone or in combination with other therapeutic modalities in the treatment of many skin diseases. The purpose of the injection is to attain a high local concentration of the CS at the diseased site, without significant systemic absorption, thus avoiding the numerous side-effects associated with systemic administration. Intralesional CS injection may be a valuable therapeutic modality in situations where topical CS are not suitable for use, either because of low potency and inefficient epidermal barrier penetration or in clinical conditions associated with epidermal atrophy.

Effects of topical treatment with budesonide on parameters for epidermal proliferation, keratinization and inflammation in psoriasis

Corticosteroids are important in the treatment of inflammatory dermatoses, such as psoriasis. They have anti-inflammatory, anti-proliferative and immunosuppressive effects. In this study, the effect of budesonide on proliferation, inflammatory cells and cytokines in psoriasis was investigated. In order to elucidate the time course of the different effects of corticosteroid treatment in psoriasis, six patients were treated for 3 weeks with budesonide 0.025% ointment (Preferid), and biopsies were studied immunohistochemically, before treatment and after 1 and 3 weeks of treatment. Clinical scores together with staining with antibodies indicating proliferation, keratin 16, keratin 10, T-lymphocytes, monocytes, polymorphonuclear leukocytes, Langerhans cells, interleukin-1alpha (IL-1alpha), interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-alpha), and intercellular adhesion molecule-1 (ICAM-1) were performed. 'Psoriasis area' and 'severity index' (PASI) scores were significantly reduced after 1 week and 3 weeks of treatment. Epidermal hyperproliferation (Ki-67 binding) and suprabasal keratin 16 (Ks8.12) expression decreased within 1 week, while keratin 10 (RKSE60) expression did not change. Five out of 6 patients showed cytokine levels (IL-1alpha, IL-6, IL-8, and TNF-alpha; detected immunohistochemically) in the normal range, while 1 patient had highly increased cytokine levels. In this patient, cytokine levels decreased during treatment. In 4 patients, showing high dermal ICAM-1 expression before treatment, a consistent reduction of ICAM-1 on endothelial cells was observed. The inflammatory infiltrate (T-lymphocytes (T11), monocytes/macrophages (WT14), polymorphonuclear leukocytes (PMN, anti-elastase)) was reduced to some extent after 3 weeks. The number of Langerhans cells (OKT6) did not change. These results indicate that the psoriatic lesions, although clinically comparable, show interindividual differences in cytokine expression. Corticosteroid treatment for 1-3 weeks improves clinical scores and hyperproliferation. Cytokine levels are reduced during steroid treatment in the patient who showed high levels before treatment. To suppress the infiltrate entirely, longer steroid treatment is probably necessary. This may explain the relapse seen after short term corticosteroid therapy.

Effect of 3 months' nasal steroid therapy on nasal T cells and Langerhans cells in patients suffering from allergic rhinitis

The effect of nasal corticosteroid therapy on allergic rhinitis is uncertain. In a double-blind, placebo-controlled study over 3 months, we investigated the influence of a new corticosteroid spray, fluticasone propionate aqueous nasal spray (FPANS), on Langerhans cells (CD1a+ cells), HLA-DR+ cells, and T cells in nasal mucosa. Efficacy was evaluated by nasal symptom score. This treatment significantly decreased the number of CD1a+ cells and HLA-DR+ cells in the nasal mucosa. Furthermore, a clear trend of decreasing numbers of T cells in nasal epithelium was found. No change in nasal symptom score was found after the treatment period. These findings suggest that fluticasone propionate aqueous nasal spray decreases the antigen presentation in nasal allergy.

African swine fever interference with foot-and-mouth disease infection and seroconversion in pigs

Initial oral infection of pigs with either highly virulent (L-60) or moderately virulent (DR-2) African swine fever virus (ASFV), followed in 3 days with exposure to foot-and-mouth disease virus (FMDV) (tongue inoculation and contact), failed to cause FMDV infection or seroconversion in 18 of 22 L-60-infected pigs and 13 of 34 DR-2-infected pigs. Of the 13 DR-2-infected pigs remaining free of foot-and-mouth disease (FMD), 2 pigs survived to 24 days without antibody to FMDV, despite constant contact with clinically infected pigs with FMD. Three other DR-2-infected pigs never developed FMD lesions but did develop low levels of antibody to FMDV by day 17. A group of larger pig (in which DR-2 is less virulent) infected with DR-2 and then FMDV had a rapid but suppressed immune response to FMDV. Contact pigs introduced 3 days postinoculation and inoculated with FMDV only all became infected with ASFV by contact and died. This remarkably long lasting 1-way interference with FMD infection during acute and subacute African swine fever was not anticipated. Infection with ASFV may have blocked the initial target cells (possibly dendritic cells) necessary for establishment of FMDV infection.

Horizons in pharmacologic intervention in allergic contact dermatitis

The treatment of allergic contact dermatitis remains a major challenge. Current management strategies consist of elimination of the allergen when possible and therapy for symptoms with topical or systemic corticosteroids. With increasing exposure of the human skin to environmental antigens and haptens, more selective treatment options are needed. Advances in the elucidation of the skin immune system and of the cellular and molecular events in immunologic processes may allow targeted methods of controlling delayed hypersensitivity reactions. This review focuses on mechanisms of established therapeutic agents and new developments, such as FK 506 (tacrolimus), pentoxifylline, and vitamin D3 derivative, for suppression of any phase of allergic contact dermatitis.

Immunohistochemical appearance of corticosteroid contact hypersensitivity reactions

We have studied, immunohistochemically, hypersensitivity reactions to corticosteroids and compared them with allergic contact dermatitis from nickel and appropriate controls. We could find no qualitative differences between nickel and corticosteroid contact reactions, providing further evidence that hypersensitivity to corticosteroids is an immunologically mediated reaction.

Immune events in skin. I. Spontaneous cluster formation of dendritic (veiled) cells and lymphocytes from skin lymph

To investigate the mechanism of spontaneous attachment of afferent lymph lymphocytes to dendritic cells, cells from canine skin lymph were used. There were 3.3 +/- 2.8% of veiled cells in clusters found in lymph flowing from the cannulated lymph vessel. The number of clusters forming ex vivo in the collected lymph samples increased as a function of time and was temperature dependent. Incubation of cells with proteolytic enzymes or monosaccharides did not alter cell interactions. The ability of veiled cells to bind lymphocytes was independent of divalent cations but reduced by xylocaine and retinoic acid. Among steroids only methylprednisolone showed an inhibitory effect on cluster formation. Indomethacin and acetylsalicylic acid had no blocking activity on cell binding. Also, no effect was seen after treatment with cyclosporine A and azathioprine. An enhanced cluster formation after desialation with neuraminidase was observed. The desialated cells were cultured in order to study their stimulatory and accessory cell functions. No enhancement of autologous mixed leucocyte reaction was seen, but a significantly higher responsiveness to a suboptimal dose of phytohaemagglutinin was observed. The N-ase-mediated non-specific cell attachment could be abrogated by cell washing or treatment with EDTA or xylocaine. This study indicates that cluster formation by skin lymph veiled cells and lymphocytes is a spontaneous process which cannot be controlled by means usually effective in regulating the in vitro induced clustering of antigen-stimulated cells.

Epidermal cytokeratin and immunocyte responses during treatment of psoriasis with calcipotriol and betamethasone valerate

Changes in epidermal immunocytes and cytokeratins were investigated during treatment of psoriasis with calcipotriol and betamethasone valerate. Skin biopsies were obtained from 10 subjects on each treatment from lesional and non-lesional skin at baseline, and from treated lesions after 4 weeks. In each subject, changes in expression of cytokeratins K5, K10 and K16, and changes in epidermal immunocyte counts were assessed. Responses were compared with a separate histological parameter of improvement, epidermal thickness. Both treatments produced a marked normalization of cytokeratins. The reduction of K16 expression was similar on each treatment and correlated significantly with reduction in epidermal thickness. Expression of both K5 and K10 improved less than thickness with betamethasone valerate but more than thickness with calcipotriol, although these differences did not reach statistical significance. With calcipotriol there was an increase in K5 and K10 responses with increasing response of epidermal thickness, which was not seen with betamethasone valerate. T6+ cells, HLA-DR+ dendritic cells and T lymphocytes were all reduced by betamethasone valerate. There was a remarkable similarity in the level of normalization between cell types and also between cellular response and reduction in thickness. Calcipotriol produced a similar consistent reduction in cell numbers and in thickness, with the exception of T6+ cells which increased in some subjects during treatment. Only in subjects in whom thickness had virtually returned to normal was there a marked decrease in T6+ cells.

Counts of S-100 positive epidermal dendritic cells in Kveim test skin biopsies

S-100 positive epidermal dendritic cells were counted in skin biopsies from 48 Kveim tests and four known foreign-body reactions. Counts in histologically positive Kveim biopsies (mean 11.3 per 200 basal cells) were significantly higher than in either negative biopsies (5.1; P less than 0.001) or foreign-body reactions (4.7; P less than 0.05). A similar difference was found, irrespective of the histological appearances, between biopsies from patients diagnosed clinically as having sarcoidosis (10.5) and those in which another diagnosis had been made (4.1; P less than 0.001). In biopsies from patients with sarcoidosis 70% had a positive Kveim test, 70% had a raised epidermal dendritic cell count and one or the other was positive in 90%. All cases in which both the Kveim test was positive and the dendritic cell count was raised had a final clinical diagnosis of sarcoidosis. Counts of S-100 positive epidermal dendritic cells are useful in differentiating positive reactions to Kveim suspension from non-specific reactions to foreign material and increase the diagnostic confidence of the Kveim test.

Langerhans cell depletion in gliotoxin-treated murine epidermis

Langerhans cells (LC) are dendritic antigen presenting cells of bone marrow origin which reside in the suprabasal layer of the epidermis. They express high concentrations of Class II MHC glycoproteins on their plasma membrane and transport cutaneous antigen to local lymph nodes for presentation to helper T cells. They are thus essential for the induction of cutaneous immunity. Gliotoxin is a member of the epipolythiodioxopiperazine (ETP) group of fungal metabolites, derived from the human pathogen Aspergillus fumigatus. It has been shown to have immunomodulating properties in vivo and in vitro, and has been proposed as a potential immunosuppressant for transplantation therapy. Epicutaneous application of gliotoxin reduced the numbers of epidermal LC by 30-35 per cent with an associated morphological change from highly dendritic to a more rounded form. Electron microscopic studies showed selective damage to LC at very low (nM) concentrations of gliotoxin, with no obvious effect on adjacent keratinocytes. LC numbers remained depleted for 13 weeks after initial treatment, suggesting that systemic suppression or prolonged retention of gliotoxin within the skin may play a role in its mechanism of action.

Rationale for anti-AIDS chemotherapy directed at HIV-1 infected dendritic cells in seropositive individuals prior to the appearance of ARC and AIDS

An approach to anti-AIDS chemotherapy is presented from the point of view of treating seropositive individuals by eliminating the infected dendritic cells that are the in vivo target of HIV-1. Special attention is given to the treatment of Langerhans (dendritic) cells in the skin and epithelia that are infected in vivo by HIV and are involved in the development of the symptoms leading to AIDS and ARC. Since HIV is released through the cervical and vaginal epithelia in seropositive women, it is suggested that combined local treatment of vaginal epithelium with steroids that inactivate dendritic cells and azidothymidine (AZT) that inhibits HIV-1 replication might prevent virus dissemination. Abrogation of HIV-1 transmission will help to prevent its spread throughout the heterosexual population. Thus a new rationale for anti-AIDS treatment is presented, namely selective elimination of HIV-1 infected dendritic cells in the skin and epithelia of infected individuals before the appearance of ARC or AIDS. Subsequent restoration of dendritic cells in HIV-1-infected persons (and in AIDS patients) by means of orally administered retinoids in combination with an antiviral drug might be a useful approach to prevent or delay AIDS.

A study of systemic and topical effects of topical steroid application through the comparison of two application schedules

We compared two application schedules of a topical steroid, BV (Betamethasone valerate). The schedules were once daily and twice a week on juvenile Wistar rats treated for four weeks. Steroid actions were assessed topically (skin thickness and epidermal Langerhans cell density) and systemically (body weight and internal organ wet weights). The results revealed some rather severe systemic effects caused by frequent steroid application. And we also found a uniquely weak BV effect with Langerhans cells compared to obvious systemic effects on rats. We came to the conclusion that frequent steroid application to the young should be avoided.

Contact allergy to corticosteroids: a frequently missed diagnosis?

Contact allergy to corticosteroids is more prevalent than previously recognized and often goes undetected. Nineteen patients with corticosteroid contact allergy are presented. Sixteen reacted to tixocortol pivalate and also to other corticosteroids, particularly to hydrocortisone, which could explain exacerbations of eczema in these cases. Tixocortol pivalate may be a useful marker for screening patients for contact sensitivity to several corticosteroids.

Flow cytometric analysis and sorting of HLA-DR+CD1+ Langerhans cells

There is a considerable need for reliable methods for enumeration and enrichment of Langerhans cells (LCs), since they continue to be the subject of intensive investigation in normal and diseased skin. It has been claimed that standard labelling with either anti-HLA-DR or OKT6 antibodies alone may fail to identify potentially important subsets of LCs with the phenotypes HLA-DR+CD1- and HLA-DR-CD1+. We report here on flow cytometric analysis of suction blister-derived normal epidermal cell (EC) suspensions, double stained with phycoerythrin-conjugated anti-HLA-DR and fluoresceinated OKT6. In seven separate experiments, no evidence for the existence of either HLA-DR+CDI- or HLA-DR-CDI+ ECs was obtained. We found that HLA-DR+CDI+LCs, which constituted a mean of 2.5% (+/- 0.3 SEM) of all ECs, could be readily identified on the basis of fluorescence, and that their light scatter characteristics were those of moderately sized cells of low granularity. We further describe our method for flow cytometric enrichment of such HLA-DR+CDi+ LCs for functional studies, based on selection on both fluorescence and light scatter criteria. Enrichment is to greater than 90% purity, and the method is applicable to the small number of ECs (approximately 1 x 10(6] obtained from a suction blister.

PUVA therapy decreases HLA-DR+ CDIa+ Langerhans cells and epidermal cell antigen-presenting capacity in human skin, but flow cytometrically-sorted residual HLA-DR+ CDIa+ Langerhans cells exhibit normal alloantigen-presenting function

We have investigated the effects of PUVA therapy on human Langerhans cell (LC) immunophenotype and function. Epidermal sheets were obtained from exposed, and control shielded, forearm skin at the end of a course of PUVA therapy, in patients receiving treatment routinely for a variety of dermatoses. PUVA therapy decreased the overall number of HLA-DR+CDIa+ LCs in epidermal sheets, and in epidermal cell (EC) suspensions examined using a fluorescence activated cell sorter (FACS). PUVA therapy also reduced the overall EC allostimulatory capacity in the allogeneic epidermal cell-lymphocyte reaction (ELR), and the capacity of ECs to present tetanus toxoid to, and augment concanavalin A-mediated stimulation of, lymphocytes in the autologous ELR. Depressed allostimulation by ECs from PUVA-treated skin could not be restored by indomethacin (added to block prostaglandin synthesis). The reductions in LC numbers and EC allostimulatory capacity varied according to dose, and time since cessation, of PUVA therapy, and in individual patients were of comparable degree. By contrast, the allostimulatory capacity of residual LCs from PUVA-treated skin (purified using the FACS) did not differ from that of purified control LCs. PUVA-induced suppression of cutaneous immune responses, therefore, results at least in part from an overall impairment of EC antigen-presenting capacity. Residual HLA-DR+CDIa+ LCs in PUVA-treated skin which retain their alloantigen-presenting function may represent a subgroup of PUVA-resistant LCs; alternatively, these cells may be as yet unaffected because they have only recently migrated into the epidermis.

Flow cytometrically-sorted residual HLA-DR+T6+ Langerhans cells in topical steroid-treated human skin express normal amounts of HLA-DR and CD1a/T6 antigens and exhibit normal alloantigen-presenting capacity

Topical corticosteroids decrease the number of HLA-DR+T6+ Langerhans cells (LCs) and the antigen-presenting capacity of epidermal cells (ECs). We have investigated the properties of residual HLA-DR+T6+ LCs in steroid-treated human skin. Flow cytometric analysis revealed that clobetasol propionate 0.05% applied twice daily for 7 d reduced the percentage of HLA-DR+T6+ LCs in EC suspensions to 46% of control (from a mean percentage +/- sem of 2.49 +/- 0.30 in control skin to 1.15 +/- 0.22 in steroid-treated skin), but did not significantly alter the relative amounts of HLA-DR and CD1a/T6 antigens per individual HLA-DR+T6+ cell. HLA-DR+T6- and HLA-DR-T6+ cells were not detected in either group. Steroid therapy significantly decreased the allostimulatory capacity of unsorted ECs. By contrast, in parallel experiments in which the same EC suspensions were greatly enriched (85% to 90%) for HLA-DR+T6+ LCs by flow cytometric sorting, the allostimulatory capacity of purified LCs from steroid-treated skin was not significantly different from control. Residual HLA-DR+T6+ LCs, which preserve their antigenic markers and alloantigen-presenting function, may be relatively unaffected because they have only recently immigrated into the epidermis, or they may represent a subgroup of steroid-resistant LCs. Alternatively, given the dose response relationship between topical steroid potency and decrease in HLA-DR+T6+ LC numbers, the apparent steroid resistance of residual HLA-DR+T6+ LCs may reflect heterogenity in the density of expression of LC steroid receptors.

Effects of topically applied glucocorticosteroids on patch test responses and recruitment of inflammatory cells in allergic contact dermatitis

The effects of repeated topical application of a strong glucocorticosteroid (GCS) on patch test responses and the inflammatory infiltrate were studied in twenty nickel allergic patients. Patch test responses were strongly inhibited in 18 out of 20 patients. Immunohistochemical analysis revealed marked reductions in CD1+(T6+) Langerhans cells, activated inflammatory T cells and of mast cells in the skin. It is concluded that GCS suppress contact allergic responses by reduction, or functional inhibition of antigen presenting cells. The reduced number of mast cells release less vasoactive mediators, inhibiting recruitment of inflammatory cells.