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Background House dust mites (HDMs) represent significant indoor allergen sources for patients with atopic dermatitis (AD). Subcutaneous allergen-specific immunotherapy (SCIT) has been shown to be successful in patients with allergic rhinitis and mild asthma and might represent an attractive therapeutic option for the long-term treatment of HDM sensitizations in AD patients. However, only a few studies have been conducted on the effectiveness of HDM SCIT in AD, resulting in controversial clinical results. Data on immunological changes induced by SCIT in AD patients are rare. Objectives We performed an open pilot study to assess clinical changes and objective laboratory parameters and evaluate the benefit of HDM SCIT in 25 AD patients with IgE-mediated sensitization against HDM. Methods The severity of AD was evaluated by the severity scoring of atopic dermatitis system (SCORAD). Specific IgE and IgG4 against HDM and serum levels of TARC/CCL17, MDC/CCL22, IL-16, IL-4, IFN-γ, IL-10 and TGF-β1 were measured during SCIT. Results Subjective and objective SCORAD improved significantly within only 4 weeks of treatment. The level of the tolerogenic cytokine IL-10 increased, whereas CCL17 and IL-16 decreased in the sera of the patients during SCIT. Allergen specific IgE decreased, while IgG4 increased during SCIT. Conclusion In this open-label pilot study, SCIT with an HDM extract in patients with AD led to a significant improvement of AD mirrored by a reduction of SCORAD as well as serological and immunological changes, which might serve as valuable parameters to estimate the therapeutic effect of SCIT. [ABSTRACT FROM AUTHOR]

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan (TRP)-catabolizing enzyme with regulatory effects on T cells. T cell inhibition is achieved through both TRP depletion and TRP metabolite accumulation in specific local tissue microenvironments. The expression of IDO activity by different types of antigen-presenting cells (APCs) has been shown to play a role in many instances of immunoregulation and tolerance induction. Induction of IDO after the engagement of the high-affinity receptor for IgE, FcℇRI, on atopic monocytes has been suggested to regulate T cell responses in atopic disorders. Interleukin-10 (IL-10), a cytokine known for its down-regulatory functions in the immune system, has recently been associated with the stable expression of IDO in mature tolerogenic dendritic cells. This study was devised to understand the role of systemic IDO and IL-10 in the prevention of clinical apparent allergy. The concentration of TRP and the break-down product kynurenine were measured by high-performance liquid chromatography in- and off-season in sera from patients with seasonal allergic rhinitis ( n=12) and from clinically asymptomatic atopic patients sensitized to specific aeroallergens ( n=12). Non-atopic (NA) individuals ( n=12) served as control. The concentration of plasma IL-10 was determined in parallel from these donors by ELISA in- and off-season. In clinically unresponsive but aeroallergen-sensitized atopic individuals significantly higher systemic activity of IDO and increased plasma IL-10 levels were found during allergen exposure but not off-season compared to symptomatic atopic individuals with allergic rhinitis and NA individuals. Enhanced systemic IDO activity as well as increased systemic levels of IL-10 may contribute to the containment of allergic T cell responses and could be involved in the maintenance of a state of clinical unresponsiveness. [ABSTRACT FROM AUTHOR]