Background -The pathogenesis of canine atopic dermatitis (AD) is complex. Dysregulation of the cutaneous immune system is considered to be an important part of the allergic response. Exploration of association of interleukin-17 (IL-17), IL-31, IgE and leukogram attributes with canine AD could provide novel insights into its immunopathology.Hypothesis/Objectives -To investigate possible associations of IL-17, IL-3, IgE and leukogram attributes of canine AD.Animals -17 dogs diagnosed with AD and six healthy dogs.Methods and materials -Circulating concentrations of IL-17, IL-31 and total IgE from sera samples were determined using commercial canine-specific quantitative immunoassay kits. Complete blood cell counts were analysed by an automated haematology analyser. Statistical differences between the two groups were determined using an unpaired t-test. The degree of relationship between the IL-17, IL-31, IgE, total leukocyte count (TLC) values and clinical signs scores (Canine Atopic Dermatitis Lesion Index and pruritus Visual Analog Scale pVAS) was determined by Pearson's r correlation statistic.Results -Dogs with AD had significantly (P < 0.0001) higher circulating concentrations of IL-17, IL-31 and total IgE compared with healthy dogs. Dogs with AD also had significantly higher TLC (P < 0.0002), absolute neutrophils (P < 0.0001) and absolute eosinophils (P < 0.0001) counts, and percentage of neutrophils (P < 0.03) and eosinophils (P < 0.0001) compared with healthy controls. A significant positive correlation (r 2 = 0.396; P < 0.007) between the pVAS and IL-31 was observed in dogs with AD.Conclusions and clinical importance -Marked elevation in circulating IL-17, IL-31 and total IgE along with the abnormalities in leukogram may be associated with canine AD and could be possible targets in the therapeutic management of canine AD.

Atopic dermatitis (AD) is one of the most common skin diseases of dogs. Defects in the skin barrier and overproduction of inflammatory cytokines may be the pathogenesis of canine AD. Therefore, the present study was aimed to quantify the gene expression of certain skin barrier proteins and inflammatory cytokines in dogs with AD. Eleven dogs with AD and three healthy dogs were included in the present study. The skin barrier proteins, namely Filaggrin (FLG) and Involucrin (IVL), gene expression was quantified by Real-time PCR in the lesional skin tissues of the atopic dogs and normal skin of the healthy dogs. In addition to the skin proteins, the gene expressions of the interleukin (IL)-13, IL-31, and tumour necrosis factor (TNF)-α were also quantified in the peripheral blood mononuclear cells (PBMCs) of these dogs. Compared to the healthy dogs, significantly higher (P ≤ 0.01) FLG gene expression and significantly (P ≤ 0.05) lower expression of the IVL gene were quantified in the skin of atopic dogs. Further, the dogs with AD revealed significantly higher expression of TNF-α (P ≤ 0.01), IL-31 (P ≤ 0.05), and IL-13 (P ≤ 0.05) as compared to the healthy dogs. The findings of our present study evidently suggest significantly increased and decreased expressions of FLG and IVL genes, respectively, which may be responsible for disruption of the skin barrier in dogs with AD. While, the over-expressions of TNF-α, IL-31, and IL-13 genes might be attributed to the clinical pathology and manifestations of AD in dogs. However, further studies are warranted to substantiate our hypothesis about pathogenesis and clinical manifestation of AD in dogs by including a large number of animals.

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