Langerhans cell hyperplasia and IgE expression in canine atopic dermatitis

The Acari Hypothesis, III: Atopic Dermatitis

Atopic dermatitis is a chronic relapsing dermatopathology involving IgE against allergenic materials present on mammalian epithelial surfaces. Allergens are as diverse as pet danders, and polypeptides expressed by microbes of the mammalian microbiome, e.g., Malassezia spp. The Acari Hypothesis posits that the mammalian innate immune system utilizes pathogen-bound acarian immune effectors to protect against the vectorial threat posed by mites and ticks. Per The Hypothesis, IgE-mediated allergic disease is a specious consequence of the pairing of acarian gastrointestinal materials, e.g., allergenic foodstuffs, with acarian innate immune effectors that have interspecies operability. In keeping with The Hypothesis, the IgE profile of atopic patients should include both anti-acarian antibodies and specious antibodies responsible for specific allergy. Further, the profile should inform on the diet and/or environment of the acarian vector. In this regard, the prevalence of Demodex and Dermatophagoides on the skin of persons suffering from atopic dermatitis is increased. Importantly, the diets of these mites correspond well with the allergens of affected patients. In this report, roles for these specific acarians in the pathogenesis of atopic dermatitis are proposed and elaborated.

Cannabinoid receptors in the inflammatory cells of canine atopic dermatitis

Background

Atopic dermatitis (AD) is one of the most common cutaneous inflammatory and pruritic diseases in dogs. Considering its multifactorial nature, AD can be a challenging disease to manage, and the therapeutic strategy must often be multimodal. In recent years, research has been moving toward the use of natural products which have beneficial effects on inflammation and itching, and no side effects. Cannabinoid receptors have been demonstrated to be expressed in healthy and diseased skin; therefore, one of the potential alternative therapeutic targets for investigating AD is the endocannabinoid system (ECS).

Objective

To immunohistochemically investigate the expression of the cannabinoid receptor type 2 (CB2R), and the cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) in mast cells (MCs), macrophages, dendritic cells (DCs), T cells, and neutrophils of the skin of dogs with AD.

Animals

Samples of skin tissues were collected from eight dogs with AD (AD-dogs).

Materials and methods

The immunofluorescent stained cryosections of the skins of 8 dogs with AD having antibodies against CB2R, GPR55, TRPV1, TRPA1 were semiquantitatively evaluated. The inflammatory cells were identified using antibodies against tryptase (mast cells), ionized calcium binding adaptor molecule 1 (IBA1) (macrophages/DCs), CD3 (T cells), and calprotectin (neutrophils). The proportions of MCs, macrophages/DCs, T cells, and neutrophils expressing CB2R, GPR55, TRPV1 and TRPA1 were evaluated.

Results

The cells of the inflammatory infiltrate showed immunoreactivity (IR) for all or for some of the cannabinoid and cannabinoid-related receptors studied. In particular, MCs and macrophages/DCs showed CB2R-, GPR55-, TRPA1-, and TRPV1-IR; T cells showed CB2R-, GPR55- and TRPA1-IR, and neutrophils expressed GPR55-IR. Co-localization studies indicated that CB2R-IR was co-expressed with TRPV1-, TRPA1-, and GPR55-IR in different cellular elements of the dermis of the AD-dogs.

Conclusions and clinical importance

Cannabinoid receptor 2, and cannabinoid-related receptors GPR55, TRPV1 and TRPA1 were widely expressed in the inflammatory infiltrate of the AD-dogs. Based on the present findings, the ECS could be considered to be a potential therapeutic target for dogs with AD, and may mitigate itch and inflammation.

Inhibitory Effects of Donkey Hide Gelatin on DNCB-Induced Atopic Dermatitis in NC/Nga Mice

The increase of atopic dermatitis has led to higher socio-economic cost and raised a need for alternative medicine as novel therapeutic agents. In this study, we aimed to evaluate the inhibitory effects of Donkey Hide Gelatin (DHG) water extract on DNCB-induced atopic dermatitis in NC/Nga mice and on tumor necrosis factor (TNF)-α/interferon (IFN)-γ-treated keratinocytes and to investigate its underlying molecular mechanisms. NC/Nga mice were induced by DNCB, administered Dexamethasone (3 mg/kg) or DHG water extracts (100–400 mg/kg) for 3 weeks. The skin symptom score, serum IgE and immune cells were measured, the ALN, spleen and dorsal skin tissue were extracted for FACS, quantitative real-time PCR and histology analysis. In vitro, HaCaT cells were induced by TNF-α/IFN-γ, the levels of pro-inflammatory cytokines and chemokines and its underlying mechanism were measured by ELISA and Western blot. As a result, DHG groups showed a significant decrease in the skin symptom score and the immune cell absolute number. It also showed a marked reduction of allergic and the levels of neutrophils and eosinophils in histology analysis. In TNF-α/IFN-γ induced HaCaT cells, DHG showed inhibition effects on IL-6, IL-8, TARC and RANTES, it also downregulated the expression of ICAM-1 and COX-2, up-regulated the expression of Filaggrin. Furthermore, DHG suppressed the activation of NF-κB and mitogen-activated protein kinases (MAPK) signaling pathway induced by TNF-α/IFN-γ. Taken together, DHG maybe a potential therapeutic agent or supplement for skin inflammatory disease such as atopic dermatitis.

Current views on neuropeptides in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease involving skin barrier dysfunction and immune imbalance. However, the mechanism of AD is not clear completely and may be related to heredity and environment. Neuropeptides are a class of peptides secreted by nerve endings, they may play roles in promoting vasodilation, plasma extravasation, chemotaxis of inflammatory cells and mediating pruritus. Since itching and immune cell infiltration are the main manifestations of atopic dermatitis, to further investigate the impact of neuropeptides on AD, our review summarized the mechanisms of several common neuropeptides in AD and hypothesized that neuropeptides may be the novel potential targets in AD treatment.

Zinc in Dog Nutrition, Health and Disease: A Review

Simple Summary

This work compiles the current state of knowledge regarding zinc requirements of healthy dogs and biomarkers of zinc status. To ensure an adequate zinc status, it is important to know the zinc content of foods and their bioavailability to assess the need and the ideal supplementation strategy regarding levels and sources of additives in complete dog foods. As zinc is required for enzymatic, structural, and regulatory functions in the animal body, its nutritional status has been associated with several pathologies that may be due to, or exacerbated by, a deficit of dietary zinc supply.

Abstract

Zinc is an essential trace element, required for enzymatic, structural, and regulatory functions. As body reserves are scarce, an adequate zinc status relies on proper dietary supply and efficient homeostasis. Several biomarkers have been proposed that enable the detection of poor zinc status, but more sensitive and specific ones are needed to detect marginal deficiencies. The zinc content of commercial dry dog foods has great variability, with a more frequent non-compliance with the maximum authorized limit than with the nutritional requirement. The bioavailability of dietary zinc also plays a crucial role in ensuring an adequate zinc status. Despite controversial results, organic zinc sources have been considered more bioavailable than inorganic sources, albeit the zinc source effect is more evident after a restriction period of dietary zinc. Many disorders have been associated with inadequate zinc status, not being clear whether the occurrence of the disease is the consequence or the cause. This review presents data on zinc requirements and biomarkers for zinc status, that can be applied for the development of supplementation strategies of zinc in complete pet foods. Moreover, it provides an understanding of the role zinc plays in the health of dogs, and how altered zinc status affects diseases in dogs.

Immunopathogenesis of the feline atopic syndrome

BACKGROUND

Feline diseases of possible allergic origin with similar clinical phenotypes can have a varied underlying pathogenesis. Clinical phenotype, precise aetiology and underlying immunopathogenesis all need to be considered if advances in this neglected area of dermatology are to be made.

OBJECTIVES

To document the status of research into the immunopathogenesis of the diseases that fall within the spectrum of the feline atopic syndrome (FAS ), to summarize the conclusions, identify the limitations and recommend future research directions.

METHODS AND MATERIALS

A search of the literature was undertaken. The strengths and validity of the data and the contributions to our current understanding of the immunopathogenesis were analysed. Skin diseases of presumed allergic aetiology and asthma were assessed separately, as was the role of antibodies, cells and cytokines in each.

RESULTS

The research varied in its quality and its impact often was limited by a failure to employ strict criteria in case selection. This reflected the difficulties of skin reaction patterns associated with a number of inciting causes. Research into feline asthma was handicapped by the difficulties of investigating clinical material, and much of the useful information was derived from experimental models.

CONCLUSIONS AND CLINICAL IMPORTANCE

The evidence reviewed was supportive of a role for immunoglobulin (Ig)E in the pathogenesis of both feline atopic skin syndrome (FASS) and asthma, albeit not strongly so. The inflammation noted in both FASS and asthma is accompanied by eosinophils and lymphocytes, and these findings, together with the cytokine expression, are suggestive in some (not all) cats of T-helper type 2 immune dysregulation.

Urban environment predisposes dogs and their owners to allergic symptoms

Our companion-animals, dogs, suffer increasingly from non-communicable diseases, analogous to those common in humans, such as allergic manifestations. In humans, living in rural environments is associated with lower risk of allergic diseases. Our aim was to explore whether a similar pattern can be found in dogs, using a nation-wide survey in Finland (n = 5722). We characterised the land-use around dog's home at the time of birth as well as around its current home, and described several lifestyle factors. The severity of owner-reported allergic symptoms in dogs was estimated with a comprehensive set of questions, developed by experts of canine dermatology. Also, the prevalence of diagnosed allergies in dog owners was recorded. The results indicate that allergic symptoms are more prevalent in urban environments both in dog owners and in dogs (accounting the effect of dog breed). Several factors related to rural living, such as bigger family size and regular contact with farm animals and other pets, were also protective against allergic symptoms in dogs. Interestingly, allergic dogs were more likely to have allergic owners than healthy dogs were. Therefore, we suggest that the mutual presence of allergic symptoms in both species indicates common underlying causal factors of allergic diseases.

Evaluation of intraepidermal nerve fibres in the skin of normal and atopic dogs

BACKGROUND

Interest in intraepidermal nerve fibres (IENFs) is rising in human medicine, because variations in fibre density occur in some diseases and these neurites might contribute to disease pathogenesis. An increase in IENF density is seen in human atopic dermatitis (AD); there are no such data in atopic dogs.

OBJECTIVES

To compare the prevalence of IENFs in normal and atopic canine skin.

METHODS

Eight millimetre skin punch biopsies were taken from six sites of 25 healthy dogs without dermatitis and compared to lesional and nonlesional skin samples of dogs with AD (23 and 14 dogs, respectively). Thirty micrometre-thick paraffin-embedded sections were stained by indirect immunofluorescence for neuronal beta-3 tubulin. Only sections with detectable dermal nerves were then screened for the presence of IENFs.

RESULTS

IENFs were identified in all 25 normal nasal planum sections, but in only one biopsy collected from each of the normal canine haired skin (NCHS) sites. As there was no significant difference in IENF prevalence between NCHS areas, they were grouped together. The rate of detection of IENFs was significantly higher (one-tailed Fisher's test, P = 0.004) in lesional AD specimens (18 of 23; 78%) than in nonlesional AD (four of 14; 29%) and NCHS specimens (four of 111; 4%, P < 0.0001). The prevalence of IENF detection in nonlesional AD samples was significantly higher than in normal canine skin (P = 0.006).

CONCLUSIONS AND CLINICAL IMPORTANCE

IENFs are detected more commonly in canine AD than in normal haired skin; these results are comparable to those seen for human AD.

Sceptridium ternatum attenuates allergic contact dermatitis-like skin lesions by inhibiting T helper 2-type immune responses and inflammatory responses in a mouse model

BACKGROUND

Sceptridium ternatum (ST) is a medicinal herb used in folk remedies for the treatment of various disorders such as pertussis, allergic asthma, abdominalgia, diarrhea, and external use for wound healing. However, the biological and pharmacological activities of ST are not fully clarified besides anti-asthmatic effect.

OBJECTIVE

We studied a Sceptridium ternatum ethanol extract (ST) with respect to its anti-inflammatory and immune regulatory activities in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, concanavalin A (conA)-stimulated BALB/c mice splenocytes, and a 2,4-dinitrochlorobenzene (DNCB)-induced allergic contact dermatitis (ACD) mouse model.

METHODS

RAW 264.7 cells were pretreated with ST for 1h and then stimulated with LPS. To determine the anti-inflammatory effects of ST, the production of nitric oxide (NO), interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) were measured using an enzyme-linked immunosorbent assay (ELISA). To determine its anti-allergic effects, splenocytes from BALB/c mice were incubated and stimulated with conA in the absence or presence of ST for 48h. The production of IL-4 and interferon (IFN)-γ in culture supernatants were evaluated by ELISA. To test the effects of ST on ACD, 100μL of 1% DNCB was applied to the dorsal skin of BALB/c mice for 2 weeks, and ST was administered 2 h before DNCB application. The thicknesses of the epidermis and dermis were determined by skin histological analysis. Serum immunoglobulin (Ig) E levels, the production of IL-1β, IL-4, and IL-6 in dorsal skin tissue, and T helper (Th) 2 cytokines production of CD4(+) T cells were analyzed by ELISA. The expression of nuclear transcription factor-κB (NF-κB) both in vitro and in vivo was determined via immunoblotting.

RESULTS

In RAW 264.7 cells, ST inhibited LPS-induced inflammation mediator production and NF-κB expression. ST upregulated IFN-γ production and downregulated IL-4 production in conA-stimulated splenocytes. ST application reduced the thicknesses of the epidermis and dermis by decreasing serum IgE level and the expressions of IL-1β, IL-4, IL-6, and NF-κB in the dorsal skin of the DNCB-induced ACD model mice. Furthermore, ST treated group showed reduction of the Th2 cytokines production in activated CD4(+) T cells.

CONCLUSION

These findings not only indicate that application of ST reduced skin thickening by regulating Th 2-type allergic responses and inhibiting expression of inflammatory mediators in a DNCB-induced ACD mouse model, but also suggest that Sceptridium ternatum is a natural option for the treatment of skin inflammation.

The skin microbiome in healthy and allergic dogs

BACKGROUND

Changes in the microbial populations on the skin of animals have traditionally been evaluated using conventional microbiology techniques. The sequencing of bacterial 16S rRNA genes has revealed that the human skin is inhabited by a highly diverse and variable microbiome that had previously not been demonstrated by culture-based methods. The goals of this study were to describe the microbiome inhabiting different areas of the canine skin, and to compare the skin microbiome of healthy and allergic dogs.

METHODOLOGY/PRINCIPAL FINDINGS

DNA extracted from superficial skin swabs from healthy (n = 12) and allergic dogs (n = 6) from different regions of haired skin and mucosal surfaces were used for 454-pyrosequencing of the 16S rRNA gene. Principal coordinates analysis revealed clustering for the different skin sites across all dogs, with some mucosal sites and the perianal regions clustering separately from the haired skin sites. The rarefaction analysis revealed high individual variability between samples collected from healthy dogs and between the different skin sites. Higher species richness and microbial diversity were observed in the samples from haired skin when compared to mucosal surfaces or mucocutaneous junctions. In all examined regions, the most abundant phylum and family identified in the different regions of skin and mucosal surfaces were Proteobacteria and Oxalobacteriaceae. The skin of allergic dogs had lower species richness when compared to the healthy dogs. The allergic dogs had lower proportions of the Betaproteobacteria Ralstonia spp. when compared to the healthy dogs.

CONCLUSIONS/SIGNIFICANCE

The study demonstrates that the skin of dogs is inhabited by much more rich and diverse microbial communities than previously thought using culture-based methods. Our sequence data reveal high individual variability between samples collected from different patients. Differences in species richness was also seen between healthy and allergic dogs, with allergic dogs having lower species richness when compared to healthy dogs.

Canine atopic dermatitis - what have we learned?

Canine atopic dermatitis is a complex multifactorial disease. Here, Tim Nuttall, Maarja Uri and Richard Halliwell, representing three generations of veterinary dermatologists, describe the research underpinning our understanding of the condition and highlight its relevance to clinical practice.

Dermatophagoides farinae house dust mite allergen challenges reduce stratum corneum ceramides in an experimental dog model of acute atopic dermatitis

BACKGROUND

Ceramides are essential stratum corneum (SC) lipids and they play a pivotal role in maintaining effective cutaneous barrier function.

OBJECTIVES

The present study aimed at determining the effect of a Dermatophagoides farinae house dust mite (Df-HDM) allergen challenge on SC ceramides of atopic dogs experimentally sensitized to these allergens.

ANIMALS

Six Df-HDM-sensitized atopic Maltese-beagle dogs were used.

METHODS

Prechallenge SC was obtained by cyanoacrylate stripping. One week later, the dogs were challenged topically with Df-HDM allergens, which resulted in mild to moderate inflammation 24 h later. Two weeks after challenge, SC of lesional and nonlesional skin was obtained. Finally, SC was collected from challenge sites 2 months after lesion resolution. The different SC lipids were quantified blindly by thin-layer chromatography.

RESULTS

Significantly lower amounts of ceramides [AH], [AP], [AS], [NP], [EOP], [NS] and [EOS] were observed in lesional SC compared with prechallenge samples, while no significant effect was found on the amount of other lipids, including cholesterol and free fatty acids. The ceramide profile of nonlesional skin generally showed the same postchallenge reduction pattern. Ceramide amounts returned to normal within 2 months after lesion remission.

CONCLUSION AND CLINICAL IMPORTANCE

These findings suggest that the allergic reactions caused by Df-HDM allergens lead to a selective reduction of SC ceramides, not only at sites of inflammation but also at sites away from those of allergen application. There is normalization of ceramide amounts after inflammation subsides. These observations suggest that the deficiency of ceramides observed in canine atopic skin occurs, at least in part, secondary to inflammation.

Cells of the skin immune system in dogs with atopy

Twenty-five dogs with signs of atopic dermatitis were included in this study. Additionally, 10 healthy dogs were chosen as healthy skin controls. Skin biopsy specimens were taken from these dogs and evaluated for the following cells: basal cell layer including the number of mitotic figures in this layer, spinous cell layer, macrophages, melanocytes, mast cells and dendritic cells. Identification of mast cells and dendritic cells was performed by means of immunohistochemistry. Histological and statistical investigations showed that the number of mitotic figures in the basal cell layer as well as the number of mast cells, melanocytes, dendritic cells and macrophages was significantly higher in the skin of dogs with atopic dermatitis compared to the healthy dogs (p< 0.01). This finding indicates multilateral quantitative activation within the cellular elements of the skin immune system. Furthermore, marked morphological heterogeneity and distinct degranulation patterns observed among mast cells in atopic skin points to their significant functional activation and confirms that canine atopic dermatitis is still notably a mast cell-dependent disease.

Development of a new canine osteosarcoma cell line

Establishing a canine osteosarcoma (OSA) cell line can be useful to develop in vivo and in vitro models of OSA. The goal of this study was to develop, characterize and authenticate a new canine OSA cell line and a clone. A cell line and a clone were developed with standard cell culture techniques from a naturally occurring OSA in a dog. The clonal cell line induced a tumour after injection in RAG 1-deficient mouse. Histology was consistent with OSA. The original tumour from the dog and the tumour induced in the mouse were both reactive with vimentin and osteonectin (ON). The parent cell line and clonal cell line were reactive with ON, osteocalcin and alkaline phosphatase. Loss of heterozygosity was found in the same three microsatellite markers in the parent and clonal cell lines, and the tumour tissue grown in the mouse.

Characterization and quantification of ceramides in the nonlesional skin of canine patients with atopic dermatitis compared with controls

As in humans, there is mounting evidence in support of an abnormal skin barrier contributing to the pathogenesis of canine atopic dermatitis (AD). Studies in people with AD have associated an abnormal skin barrier with deficiencies in ceramides, which represent important components of the stratum corneum (SC) intercellular lipid lamellae. Therefore, the goal of this study was to determine if the SC of dogs with AD is deficient in ceramides compared to normal dogs. Samples of SC were obtained from nonlesional skin of the caudal abdomen of 14 patients with AD and 14 age-, breed- and sex-matched healthy controls using a cyanoacrylate stripping procedure, and the subclass and relative amount of ceramides were assessed blindly by thin layer chromatography. Paired t-tests using R statistical computer software revealed the percentage amounts of ceramides 1 and 9 were significantly lower in nonlesional skin of AD dogs compared to controls (P= 0.034 and P= 0.047, respectively), and the cholesterol percentage amount was significantly higher in AD dogs than in controls (P= 0.016). Furthermore, the cholesterol/ceramide ratio was significantly higher in the AD group with respect to controls (P= 0.014). These findings suggest that decreased amounts of ceramides in the skin of dogs with AD may be involved in the impaired barrier function of their skin.

A review of allergen-specific immunotherapy in human and veterinary medicine

This article reviews allergen-specific immunotherapy in human and veterinary medicine. Current hypotheses of possible mechanisms of actions are outlined. Indications, success rates, adverse effects and factors influencing outcome of therapy are discussed in humans, dogs, cats and horses.

Sensitization of Naive Beagles by Intradermal Injection of an Ascaris Antigen: Induction of a Model of Skin Allergy

Ascaris suum-hypersensitive beagles represent a unique model of skin allergy. Despite its suitability, the need to test numerous dogs prior to the selection of natural positive responders causes many complications. We hypothesized that the model could be induced in adult beagles by primary sensitization. Ten dogs were included in an intradermal sensitization program using ascaris antigen and were thereafter tested for cutaneous reaction. After 2 weeks, 60% developed a positive reaction that lasted for months. We therefore present a straightforward method to establish the Ascaris canine model of allergy that will extend its availability for research in cutaneous allergy immunomodulation.

Two canine CD1a proteins are differentially expressed in skin

Lipid antigens are presented to T cells by the CD1 family of proteins. In this study, we characterize the complete dog (Canis familiaris) CD1 locus, which is located on chromosome 38. The canine locus contains eight CD1A genes (canCD1A), of which five are pseudogenes, one canCD1B, one canCD1C, one canCD1D, and one canCD1E gene. In vivo expression of canine CD1 proteins was shown for canCD1a6, canCD1a8, and canCD1b, using a panel of anti-CD1 monoclonal antibodies (mAbs). CanCD1a6 and canCD1a8 are recognized by two distinct mAbs. Furthermore, we show differential transcription of the three canCD1A genes in canine tissues. In canine skin, the transcription level of canCD1A8 was higher than that of canCD1A6, and no transcription of canCD1A2 was detected. Based on protein modeling and protein sequence alignment, we predict that both canine CD1a proteins can bind different glycolipids in their groove. Besides differences in ectodomain structure, we observed the unique presence of three types of cytoplasmic tails encoded by canCD1A genes. cDNA sequencing and expressed sequence tag sequences confirmed the existence of a short, human CD1a-like cytoplasmic tail of four amino acids, of an intermediate length form of 15 amino acids, and of a long form of 31 amino acids.

Lack of detection of circulating skin-specific IgE autoantibodies in dogs with moderate or severe atopic dermatitis

Human patients with atopic dermatitis (AD) commonly exhibit IgE reactivity to cutaneous self-antigens. The presence of serum IgE autoantibodies appears to correlate with disease severity, and it is suspected to reflect or contribute to tissue damage. The objective of this study was to determine whether IgE autoantibodies specific for cutaneous antigens could be detected in the serum of dogs with AD. Serum was collected from 19 dogs with untreated moderate to severe AD and four specific-pathogen free (SPF) dogs. Indirect immunofluorescence was performed using normal canine skin collected at four different locations (concave ear, nose, medial thigh and lateral thorax), while Western immunoblotting was done using normal canine ear pinna epidermal and dermal extracts and reducing conditions. In both methods, IgE was detected using a monoclonal antibody specific for heat stable epitopes of canine IgE. At 1:10 dilution, specific IgE autoantibodies against cutaneous autoantigens were not detected, with either method, in AD and SPF canine sera. Either IgE autoreactivity is not associated with moderate to severe AD in dogs, or the methods employed herein were not sensitive enough to permit IgE autoantibody detection.

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

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

The role of mast cells in atopy: what can we learn from canine models? A thorough review of the biology of mast cells in canine and human systems

Mast cell research has largely focused on the role of these cells in the early phase of allergic reactions. However, their involvement may well extend beyond this stage, and even reach across nonallergic conditions. Mast cells from different sources have helped advance our knowledge of their biology. Although in vitro and in vivo research in this area has mainly focused on humans, such studies are limited by the extent to which cells from certain human tissues and/or human patients can be collected or studied. While rodents also provide valuable models with which to further our understanding of the behaviour of mast cells and their contribution to allergy, reported differences between human and murine mast cells, and, in some instances, the limitations of in vivo rodent models of mast cell-mediated allergic conditions, preclude their use. In this review, we introduce a relatively unknown mast cell population, that of the dog. Canine mast cells display many phenotypic and functional similarities with their human counterparts, and dogs develop spontaneous and induced allergic diseases that share clinical and pathophysiological features with the human condition. Therefore, the use of canine cells can shed light on the general role of mast cells, particularly in relation to allergic diseases given the potential of in vivo dog models within this field. Here we provide a detailed review of the data reported from in vitro and in vivo studies of canine mast cells, and compare them with results obtained in human systems. We also highlight direct evidence of the mast cell contribution to canine atopy. We conclude that the dog offers useful in vitro and in vivo models in which to investigate mast cell behaviour, and that its use should be considered when undertaking studies aimed either at elucidating the role of mast cells in health and disease, or at prescreening novel therapies prior to entry into man.

Immune dysregulation in flea allergy dermatitis—A model for the immunopathogenesis of allergic dermatitis

BACKGROUND

Flea allergy dermatitis (FAD) is a common skin disease in dogs and can be induced experimentally. It often coexists with other allergic conditions. So far no studies have investigated the quantitative production of cytokine mRNA in skin biopsies and peripheral blood mononuclear cells (PBMC) in flea allergic dogs.

OBJECTIVE

The aim of our study was to improve the understanding of the immunopathogenesis of allergic dermatitis as a response to fleabites.

MATERIAL AND METHODS

Allergic and non-allergic dogs were exposed to fleas. Before and after 4 days of flea exposure mRNA was isolated from biopsies and PBMC. Production of chymase, tryptase, IL-4, IL-5, IL-13, TNF-alpha and IFN-gamma mRNA was measured by real-time RT-PCR. The inflammatory infiltrate in the skin was scored semi-quantitatively. The number of eosinophils, mast cells (MC) and IgE+ cells/mm2 was evaluated to complete the picture.

RESULTS

FAD was associated with a higher number of MC before flea exposure and with a significant increase of eosinophils after flea exposure as compared to non-allergic dogs. The number of IgE+ cells was higher in allergic dogs before and after flea exposure. In allergic dogs mRNA for most cytokines and proteases tested was higher before flea exposure than after flea exposure. After exposure to fleas an increased mRNA production was only observed in non-allergic dogs. In vitro stimulation with flea antigen resulted in a decreased expression of most cytokines in allergic dogs before flea exposure. In contrast, in PBMC, only increased levels of IL-4 and IL-5 mRNA were observed in allergic dogs before flea exposure. However, after flea exposure and additional stimulation with flea antigen the production of mRNA for all cytokines tested was significantly increased in allergic dogs.

CONCLUSION

We demonstrated that the response in biopsies and PBMC is different and that FAD is associated with a TH2 response.

A canine model of cutaneous late-phase reactions: prednisolone inhibition of cellular and cytokine responses

Immunoglobulin E (IgE)-mediated late-phase reactions can be induced in atopic humans by intradermal injection of relevant allergens or anti-IgE antibodies. The histology of these reactions resembles that of naturally occurring atopic dermatitis. Strikingly similar responses can be induced in dogs, suggesting that a canine model could prove valuable for preclinical investigation of drugs targeting late-phase reactions. This study was designed to characterize the cellular, cytokine and chemokine responses after intradermal anti-IgE injection in untreated and prednisolone-treated dogs. Normal beagles were untreated or treated with prednisolone before intradermal injection of polyclonal rabbit anti-canine IgE or normal rabbit IgG. Biopsies were taken before injection and 6, 24 and 48 hr after injection. Samples were evaluated by histological and immunohistochemical staining, as well as by real-time quantitative polymerase chain reaction analysis. Dermal eosinophil and neutrophil numbers increased dramatically within 6 hr after injection of rabbit anti-canine IgE, and remained moderately elevated at 48 hr. The numbers of CD1c(+) and CD3(+) mononuclear cells were also increased at 6 hr. The real-time quantitative polymerase chain reaction demonstrated marked increases in mRNA expression for interleukin-13 (IL-13), CCL2, CCL5 and CCL17. Levels of mRNA for IL-2, IL-4, IL-6 and IFN-gamma did not change within the limits of detection. Prednisolone administration suppressed the influx of neutrophils, eosinophils, CD1c(+) and CD3(+) cells, as well as expression of IL-13, CCL2, CCL5 and CCL17. These data document the cytokine and chemokine responses to anti-IgE injection in canine skin, and they demonstrate the ability of the model to characterize the anti-inflammatory effects of a known therapeutic agent.

Canine epidermal langerhans cells express alpha and gamma but not beta chains of high-affinity IgE receptor

Epidermal Langerhans cells (LC) express a high-affinity receptor for IgE (FcepsilonRI), consisting of two chains (alpha and gamma chains) in humans that allows LC to perform Fc receptor-mediated uptake of allergens. We found that canine LC express alpha and gamma chains but not beta chain of FcepsilonRI, identical to human but not to mouse LC, which do not express functional FcepsilonRI (only gamma chain is expressed). This finding indicates that canine LC have FcepsilonRI-mediated function similar to or identical to human LC, raising the possibility that canine species provides a better model than mouse to understand the pathogenesis of human atopic dermatitis and investigate the therapeutic effect of drugs.

Distribution of leucocyte subsets in bronchial mucosa from dogs with eosinophilic bronchopneumopathy

Immunohistochemistry was used to characterize the distribution of leucocyte subsets in the bronchial mucosa of 11 dogs with idiopathic eosinophilic bronchopneumopathy (EBP). Formalin-fixed tissues from all dogs were included in the study, but frozen tissue from only one dog was available. MHC class II(+) cells were found in moderate numbers in the lamina propria (LP). These cells were morphologically either dendritic-like cells or macrophages, but many macrophages did not express MHC class II. Such molecules were expressed by occasional fibroblasts. L1(+) cells, which formed a relatively small component of the LP inflammatory infiltrate, were morphologically either macrophages or polymorphonuclear cells (probably eosinophils). IgA(+) plasma cells were found in varying numbers in the LP, mostly in association with glandular tissue. IgG(+) plasma cells were less common, and IgM(+) plasma cells were present in low numbers. Many CD3(+) cells were present in the LP. In the single case from which frozen tissue was available, most of the lymphocytes were labelled with CD4 marker, while smaller numbers were CD8(+) T cells. Most of the lymphocytes in this case were positively labelled with T-cell receptor (TCR)-alphabeta marker. TCR-gammadelta(+) cells, although less common, were present in significant numbers throughout the LP. CDlc(+) dendritic cells were numerous in the epithelium and in the LP, immediately beneath the basement membrane. These findings, which were similar to those described in human asthma, are suggestive of a Th2 dominant immune response in canine EBP. As in human asthma, this provides a possible basis for new forms of treatment in canine EBP.

"Dendritic cells in different animal species: an overview"

The comprehension of the immune system and the role of DC in the pathological diseases may contribute to their use in veterinary medicine in the prevention and treatment of many diseases. Currently, most dendritic cell (DC) research occurs in the human and murine model systems on the generation of cells from the bone marrow or peripheral blood mononuclear cells (PBMC) cultured in vitro. Despite the lack of available immunological reagents such as antibodies and cytokines, analogous cells have been generated and identified in many different species and reviewed in this study.

Distribution of leucocyte subsets in the canine respiratory tract

Histochemistry and immunohistochemistry were used to characterize leucocyte subsets in the respiratory tract of 15 outbred dogs (five aged <6 months and 10 aged >1 year) that had no evidence of respiratory disease. No organized nose- or bronchus-associated lymphoid tissue was observed in any of the sections examined. IgA(+) plasma cells predominated in nasal mucosa and in all parts of the bronchial tree, with fewer IgG(+) and IgM(+) plasma cells. The numbers of IgA(+) and IgM(+) cells were significantly greater in the nasal mucosa than in any other part of the respiratory mucosa. There were significantly fewer IgA(+), IgG(+) and IgM(+) cells in all parts of the respiratory tract in the puppies than in the adults. The number and distribution of mast cells and cells expressing MHC class II, L1 or CD1c were recorded. Mast cells were mainly found in the subepithelial lamina propria of nasal and bronchial mucosa and in the alveolar interstitium, and cells expressing IgE had a similar distribution. Mast cells were also present within muscle layers of the bronchial tree. The numbers of mast cells and MHC class II(+) cells were significantly greater in the nasal mucosa than in any other part of the respiratory mucosa. In the nose, carina and primary and secondary bronchus, there were significantly more mast cells and MHC class II(+) cells in puppies than in adult dogs, whereas the numbers of L1(+) cells and CD1c(+) cells in most sites were significantly greater in older dogs. There were significantly more CD3(+) and CD8(+) cells in the nasal mucosa than in any part of the bronchial mucosa. In most parts of the respiratory mucosa, CD4(+), CD8(+) and TCR alphabeta(+) cells were present in significantly greater numbers in adults than in puppies. All parts of the respiratory tract had similar numbers of mucosal CD4(+) and CD8(+) T lymphocytes. TCR gammadelta(+) cells were absent or sparse in all samples. These data, obtained from dogs without respiratory disease, will enable comparisons to be made with dogs suffering from infectious or inflammatory nasal, bronchial and pulmonary diseases.

Allergen-specific immunotherapy induces Th1 shift in dogs with atopic dermatitis

Allergen-specific immunotherapy has been applied to canine atopic dermatitis. Despite the accumulated clinical evidence of its effect for atopic dogs, the basic immunologic mechanisms were not fully understood. In this study, the cytokine profile ex vivo in canine atopic dermatitis before and after allergen-specific immunotherapy was characterized using competitive reverse transcription-polymerase chain reaction (RT-PCR). Blood samples were collected from 10 dogs with atopic dermatitis and peripheral blood mononuclear cells were stimulated with house dust mite antigen. The levels of IFN-gamma and IL-4 mRNA were lower in atopic dogs compared with non-atopic controls. The ratio of IFN-gamma/IL-4 was low in atopic dogs indicating a cytokine profile polarized to Th2. The level of IFN-gamma after immunotherapy was significantly higher than that before (P < 0.05) whereas that of IL-4 mRNA was not changed. Consequently, the ratio of IFN-gamma/IL-4 after immunotherapy was significantly higher than that before immunotherapy (P < 0.05). These results indicate a Th2 cytokine bias is the dominant state in atopic dogs and allergen-specific immunotherapy causes a shift to wards a Th1 bias by enhancing IFN-gamma expression.

Canine atopic dermatitis: new targets, new therapies

Atopic dermatitis is a common allergic skin disease of complex etiopathogenesis in both humans and dogs. Immediate-type hypersensitivity to environmental allergens that arises as a result of environmental and genetic factors is a major part of the pathogenesis in most but not all patients. Alterations in epidermal barrier function, priming of cutaneous antigen-presenting cells with IgE, intrinsic keratinocyte defects, and even development of autoimmunity are also factors that contribute to the primary disease. Secondary factors, especially infections with Staphylococcus and yeast organisms, strongly influence the course of this skin disease. The relatively recent understanding of the complexities of atopic dermatitis has resulted in changes in diagnostic and therapeutic strategies for the disease. We now know that the best therapeutic approach is to use combinations of multiple modalities individualized for each patient over the course of his or her lifetime.

Distribution of MHC II (+) cells in skin of the Atlantic bottlenose dolphin (Tursiops truncatus): an initial investigation of dolphin dendritic cells

The skin is an important tissue of the immune system; however, little is known about immune cells in dolphin skin, and very few cetacean-specific immunoreagents are available for investigative purposes. Therefore, in this study immunohistochemistry techniques were used with species-specific and non-species-specific antibodies to characterize immune cells, primarily focusing on Langerhans cells, in skin from the Atlantic bottlenose dolphin (Tursiops truncatus). An antibody to human major histocompatibility complex (MHC) class II molecules labeled cells with a dendritic-like morphology. The immunophenotype, morphology, and distribution of some of these cells are consistent with those of Langerhans cells. The cells were predominantly found in dermal papillae, primarily along the epidermal-dermal junction. Thus, the location of these cells was somewhat different from that in terrestrial mammals. Other MHC II (+) cells of varying morphology were observed deeper in the dermis, with a perivascular concentration, and had characteristics of macrophages and dermal dendritic cells. There was no immunostaining with cetacean-specific CD2 or CD21. In diseased skin, a subjective increase of MHC II (+) cells, most notably in the superficial skin layers, was associated with an ulcerative dermatitis. A few CD2 (+) cells were also present. Differences between dolphins and terrestrial mammals in terms of morphology, mechanisms of response to insult and repair, and environmental challenges may explain the modified distribution of MHC II (+) cells in dolphin skin. An elucidation of the immune cells in cetacean skin will contribute to our understanding of the evolution of functional adaptations to various environments, facilitate diagnosis of skin diseases, and define the potential for intradermal administration of vaccines and other immunotherapeutics.

Flea bite hypersensitivity: new aspects on the involvement of mast cells

A study was performed to test the effect of sensitization to flea antigen, followed by exposure to fleas on mast cells (MCs), their subtypes, and IgE+ cells. Biopsies were taken from flea-sensitized dogs (n=28) and non-sensitized dogs (n=5) that had been exposed to fleas. Control groups consisted of flea-sensitized (n=12) and non-sensitized dogs (n=9) that were not exposed to fleas. Biopsies, taken before, 24 and 72 h after local flea exposure, were stained with haematoxylin and eosin (H&E), toluidine blue, a double labelling technique for MC chymase and tryptase and anti-IgE. An intradermal test for flea antigen was performed and serum titres of allergen-specific IgE and IgG were measured. Significantly higher numbers (P<0.001) of double labelled MCs compared to toluidine blue stained MCs were detectable in flea-sensitized dogs independent of flea exposure. In contrast, in non-sensitized dogs, the number of toluidine blue stained MCs and the number of double labelled MCs did not differ. In flea-sensitized dogs after flea exposure the percentage of C-MC was significantly increased at day 1 (P<0.001) and day 3 (P<0.001), whereas the percentage of TC-MCs decreased significantly at day 1 (P<0.001) and day 3 (P<0.05). The percentage of T-MCs decreased (P<0.05 day 0 versus day 1; P<0.05 day 0 versus day 3). No significant difference was detectable after toluidine blue staining and staining for IgE+ cells between the groups nor between the MC density and the number of IgE+ cells. All flea-sensitized dogs had positive skin tests to flea antigen and high serum titres of flea-specific serum IgE and IgG antibodies. In non-sensitized dogs, these results were negative. Our data provide strong evidence for an upregulation of MC proteases during the process of sensitization and a generalized selective release of mast cell tryptase after exposure to the antigen.

Evaluation of a commercially available enzyme-linked immunosorbent assay for the detection of allergen-specific IgE antibodies in dogs

Twenty-eight atopic dogs, 22 pruritic, non-atopic dogs and 10 healthy dogs were ELISA tested. For calculations of diagnostic specificity and sensitivity, positive ELISA test results in non-atopic dogs were considered false positive results. The absence of any positive results in the atopic dogs was considered false negative results. The atopic dogs were tested both with ELISA and an intradermal test, utilising allergen extracts from the same manufacturer, to determine the frequency of positive allergen reactions in the ELISA test compared with the intradermal test. The Prausnitz-Küstner test was performed to evaluate the significance of a positive ELISA test result. Based on cross-tabulations with clinically defined atopic dermatitis, the ELISA test showed a sensitivity of 53.6% and a specificity of 84.4%. The correlation between the ELISA and the intradermal test was poor. Positive Prausnitz-Küstner tests were not obtained using sera from dogs that were intradermal test negative for the tested allergens, even though sera had high levels of IgE as measured by the ELISA. These findings question the significance of a positive ELISA test result and indicate that the test is not measuring functional allergen-specific IgE.

Langerhans cell microgranulomas (pseudo-pautrier abscesses): morphologic diversity, diagnostic implications and pathogenetic mechanisms

The term 'Langerhans cell microgranuloma' (LCM) was introduced a decade ago to draw attention to focal collections of these cells within the epidermal layer that develops during certain immune reactions. In spite of a growing awareness of this phenomenon during the past decade, few reports have focused on the development and phenotype of LCM. In this commentary, we review the historical development of the concept of LCM, demonstrate the salient immunomorphologic characteristics of LCM, and advance a hypothesis to explain their sequential evolution and formation.

Immune dysregulation in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease in humans and dogs with comparable clinical features. Comparative studies of immunological events in the pathogenesis of AD may contribute to understanding of the disease in dogs and to development and evaluation of immunomodulatory strategies of relevance to both species.Both allergen-specific as well as non-specific mechanisms contribute to the disease development. AD skin lesions are proposed to be initiated by activation of allergen-specific Th2-type cells, potentially influenced by local cutaneous factors. In the chronic stage of skin lesions reactivity may change into a Th1-type, e.g. driven by eosinophil derived IL-12. Analyses of these processes in course of time were performed in both spontaneous as well as in experimentally induced lesions (i.e. atopy patch test (APT) lesions). In the present paper, the immunological events as reported for human and canine AD are summarized and compared.

Investigation on the use of 0.3% tacrolimus lotion for canine atopic dermatitis: a pilot study

The efficacy of 0.3% tacrolimus lotion (maximum dosage: 0.3 mg kg-1 per day) for treatment of atopic dermatitis (AD) was evaluated. Systemic absorption and effects on complete blood cell counts (CBC) and chemistry panels were also investigated. Eight dogs were assigned randomly to either a tacrolimus or a vehicle lotion treatment group. Both owners and investigator were blinded to the treatment. After 4 weeks, there was a 2-week wash-out period and treatments were reversed. Owners scored pruritus weekly while the investigator scored pruritus and erythema at the beginning and end of each treatment period. Investigator scores for pruritus in the tacrolimus group significantly decreased by the end of the study (P = 0.03). Investigator scores for erythema in the tacrolimus group were significantly lower than those in the placebo group at the end of the study (P = 0.005). There was no difference between groups with respect to owner scores for pruritus. No changes in the CBC and chemistry panels were noted. Mean blood concentrations of tacrolimus were below toxic levels.