In spite of the progress regarding the description of immunological phenomena associated with atopic dermatitis (AD), the pathogenesis of this disease still remains unclear. The presence of eosinophils in the inflammatory infiltrate of AD has long been established. Eosinophil numbers as well as eosinophil granule protein levels in peripheral blood are elevated in most AD patients and appear to correlate with disease activity. Moreover, eosinophil granule proteins, which possess cytotoxic activity, are deposited in the skin lesions. These observations indicate a role of eosinophils in the pathogenesis of AD. Furthermore, AD is associated with increased production of T helper 2 cytokines including interleukin (IL)-5, which specifically acts on eosinophils, resulting in accelerated eosinophilopoiesis, chemotaxis, cell activation, and delayed apoptosis. Therefore, IL-5 is an interesting target for experimental therapy in this inflammatory disorder of the skin. Such studies might result in new insights into the pathogenetic role of eosinophils in AD.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1398-9995.2004.00476.x

Eosinophils and atopic dermatitis

House dust mite (HDM) allergens are perennial indoor allergens, which may play a role as allergic trigger factors in atopic dermatitis (AD) Facilitated by their high enzymatic activity, HDM allergens are capable of penetrating the impaired epidermal skin barrier in patients with AD, gaining access to immune cells In this way, HDM allergens induce both allergic reactions of the immediate type and allergic reactions of the delayed type, which contribute to impairment of AD Because allergen reduction achieved by encasing strategies does not always lead to significant improvement of clinical symptoms, specific immunotherapy (SIT) might represent an attractive therapeutic option for long-time treatment of this subgroup of patients with AD However, systematic studies on the effectiveness of SIT in patients with AD are rare Furthermore, data on the immunologic changes induced by SIT in patients with AD are not well studied In this review, we provide an overview of the pathogenic impact of HDM allergens as an example for aeroallergens on the course of AD In addition, we discuss prophylactic and therapeutic options for the treatment of HDM allergy in patients with AD, including a summary of the current data available on SIT as a potential therapeutic option for patients with AD

Does allergen-specific immunotherapy represent a therapeutic option for patients with atopic dermatitis?

Systemic immunosuppressive agents are recommended for patients with atopic eczema in whom disease activity cannot be controlled adequately with topical treatments. Guidelines do not give clear advice which agents to prefer. We systematically reviewed clinical trials on systemic treatment for severe atopic eczema to provide evidence-based treatment recommendations. Standardized literature search, independent standardized assessment of eligibility and data abstraction was performed by 2 reviewers. Twenty-seven studies totalling 979 patients were included. Eleven studies consistently showed effectiveness of cyclosporine. Cyclosporine is recommended as first option for patients with atopic eczema refractory to conventional treatment. Evidence from randomized controlled trials also exists for interferon-? and azathioprine. Although frequently used in clinical practice, systemic glucocorticosteroids have not been assessed adequately in studies. Mycophenolate mofetile showed effectiveness in 2 small uncontrolled studies. Intravenous immunoglobulins and infliximab are not recommended based on published data.

Systemic treatment of severe atopic eczema: a systematic review.

Among galectin family members, galectin-9 was first described as a potent eosinophil chemoattractant derived from Ag-stimulated T cells. In the present study a role of galectin-9 in the interaction between eosinophils and fibroblasts was investigated using a human lung fibroblast cell line, HFL-1. RT-PCR, real-time PCR, and Western blot analyses revealed that both galectin-9 mRNA and protein in HFL-1 cells were up-regulated by IFN-gamma stimulation. On the one hand, IL-4, known as a Th2 cytokine, did not affect the galectin-9 expression in HFL-1 cells. We further confirmed that IFN-gamma up-regulated the expression of galectin-9 in primary human dermal fibroblasts. Flow cytometric analysis revealed that IFN-gamma up-regulated surface galectin-9 expression on HFL-1 cells. Stimulation of HFL-1 cells with IFN-gamma up-regulated adhesion of eosinophils, but not neutrophils, to HFL-1 cells. This adherence of eosinophils to HFL-1 cells was inhibited by both lactose and anti-galectin-9 Ab. These findings demonstrate that IFN-gamma-induced galectin-9 expression in fibroblasts mediates eosinophil adhesion to the cells, suggesting a crucial role of galectin-9 in IFN-gamma-stimulated fibroblasts as a physiological modulator at the inflammatory sites.

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Selective eosinophil adhesion to fibroblast via IFN-gamma-induced galectin-9.

Background: Atopic dermatitis (AD) is an eczematous skin eruption that generally begins in early infancy and affects up to 12% of the population. The cause of this disorder is not fully understood, although it is frequently the first sign of atopic disease and is characterized by an elevated serum IgE level, eosinophilia, and histologic tissue changes characterized early by spongiosis and a CD4 + T H 2 cellular infiltrate. Hypersensitivity to foods has been implicated as one causative factor in up to 40% of children with moderate-to-severe AD. Objective: The purpose of this study was to establish a murine model of food-induced AD. Methods: Female C3H/HeJ mice were sensitized orally to cow's milk or peanut with a cholera toxin adjuvant and then subjected to low-grade allergen exposure. Histologic examination of skin lesions, allergen-specific serum Ig levels, and allergen-induced T-cell proliferation and cytokine production were examined. Results: An eczematous eruption developed in approximately one third of mice after low-grade exposure to milk or peanut proteins. Peripheral blood eosinophilia and elevated serum IgE levels were noted. Histologic examination of the lesional skin revealed spongiosis and a cellular infiltrate consisting of CD4 + lymphocytes, eosinophils, and mast cells. IL-5 and IL-13 mRNA expression was elevated only in the skin of mice with the eczematous eruption. Treatment of the eruption with topical corticosteroids led to decreased pruritus and resolution of the cutaneous eruption. Conclusion: This eczematous eruption resembles AD in human subjects and should provide a useful model for studying immunopathogenic mechanisms of food hypersensitivity in AD. (J Allergy Clin Immunol 2001;107:693-702.)

Murine model of atopic dermatitis associated with food hypersensitivity.

Background Interferon-gamma (IFN-gamma) therapy has been reported to be effective in atopic dermatitis. However, IFN-gamma therapy in atopic dermatitis has not yet been well established. In this study, immunologic variables were evaluated as predictors for the prognosis of IFN-gamma therapy in atopic dermatitis. Methods Sixty-eight atopic dermatitis patients were each treated 18 times with 2 x 10(6) units/m2 IFN-gamma. Blood IgE level, eosinophil percentage, eosinophil count, and levels of IFN-gamma, interleukin-4 (IL-4), IL-5, and IL-10 were investigated. According to clinical responses, patients were classified into three groups: patients with improved clinical severity scores of over 20% were included in group A; those with improved scores of 20% or less in group B; and those with no improvement in group C. Results Serum IgE levels and blood eosinophil percentages were the lowest in group A. Most atopic dermatitis patients with an eosinophil percentage over 9% and IgE level over 1500 IU/ml did not respond to IFN-gamma therapy. Initial IL-10 levels were the highest in group A. IL-4 levels in group A, and IL-5 and IL-10 levels in all groups were significantly decreased by IFN-gamma therapy. Conclusions IFN-gamma therapy may be recommended for atopic dermatitis patients with blood eosinophil percentages less than 9% and serum IgE levels less than 1500 IU/ml.

G.W. Noh

Papers

Blood eosinophils and serum IgE as predictors for prognosis of interferon-gamma therapy in atopic dermatitis.