Immune mechanisms in allergen-specific immunotherapy.

Allergen-specific immunotherapy has been shown to be clinically effective in patients with seasonal allergic rhinitis and/or asthma. Patients who receive this therapy undergo a number of specific immunologic changes in response to the allergen being administered. These include a "blunting" of the seasonal rise of allergen-specific IgE as well as lowering baseline IgE levels, generation of an allergen-specific IgG response, development of auto-anti-idiotypic antibodies, reduced basophil histamine release in response to allergen, decreased lymphocyte proliferation, lymphokine production in response to allergen, and the generation of allergen-specific suppressor T cells that down-regulate lymphoproliferative responses and IgE synthesis. The mechanism by which allergen-specific immunotherapy produces clinical efficacy is not known. Recent evidence suggests that the development of immunoregulatory responses (suppressor T cells and anti-idiotypic antibodies) during immunotherapy may account for the immunologic changes described above but as yet have not been correlated with clinical outcome. Identification of epitopes on allergens that can induce selective T helper/suppressor responses may provide opportunities for producing immunological tolerance and a reduction in the allergic diathesis.