Mechanisms of Specific Immunotherapy
Subcutaneous allergen SIT has been used most successfully in allergy to insect venoms, and in allergic rhinitis.[68–70] This mode of therapy has been shown to ameliorate allergen-induced symptoms including antibody responses (upregulation of blocking antibody responses and downregulation of allergen-specific IgE responses),[71,72] T-cell responses (reorientation of allergen-specific T-cell responses from Th2 to Th1 and/or regulatory T profile)[73–75] and inflammatory cells (reduction in the numbers and activation of proinflammatory cells such as mast cells and eosinophils).[76,77]
The oral mucosa belongs to the sophisticated network of the mucosal immune system, where tolerance induction towards a variety of antigens from commensal bacterial and nutritional products predominates to maintain local immunostasis.[19] Oral mucosal tissue demonstrates excellent wound healing without severe scar development and without acute inflammation in spite of high bacterial colonization.[78] With regards to SLIT, the tolerogenic potential of oral mucosal tissue is reflected by the lack of inflammatory cells within oral mucosal tissue after allergen administration in sensitized individuals.[79] Furthermore, oral mucosal tissue displays high permeability for allergens as it has been shown that orally applied allergen as well as monomeric allergoid retains within oral tissue for up to 20 h.[11,80,81] What then makes the oral mucosa efficient in immunological processes leading to a reduction of allergic symptoms during SLIT? It is postulated that, most likely, Langerhans-like local DCs are critically involved in this process.[68] During SLIT, the allergen is captured within the oral mucosa by Langerhans-like DCs and, subsequently, DCs mature and migrate to proximal draining lymph nodes. The significance of the role of these local lymph nodes in successful allergen SIT lies in the preferential production of blocking IgG antibodies and the induction of T lymphocytes with suppressive function.[69]
Immunotherapy. 2011;3(6):747-756. © 2011 Future Medicine Ltd.
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