[Immunological mechanisms in allergen-specific immunotherapy: impact on future trends in type-1 allergy management]

Specific immunotherapy (SIT) is the only treatment of Type-I allergy that leads to a modulation of the immune response to the eliciting allergen. The repeated administration of high doses of antigen induces a state of "antigen-specific non-responsiveness", i.e. immunologic tolerance to the injected antigen. Accordingly, during and after SIT the proliferative response of allergen-specific T lymphocytes in response to the administered antigen are significantly reduced. According to recent publications, this effect is due to the production of the immunosuppressive cytokine interleukin (IL)-10, which is induced during the treatment. On the other hand, a distinct change in the quality of the immune response to the injected allergen can be observed: the production of the IgE-inducing cytokine IL-4 by T helper cells decreases. Moreover, the release of other proinflammatory cytokines and inflammatory mediators is suppressed. Together, these events result in a marked decrease of symptoms during allergen exposure and reduced reactivity during challenge.