Healthy immune response to allergens: T regulatory cells and more.

The specific immune response to allergens is decisive in the development of clinically healthy or allergic states. In healthy individuals, the B-cell response varies between there being no response and the production of IgG(4)- or IgG(1)-dominating allergen-specific antibodies in the presence or absence of low amounts of IgE. If a detectable immune response is mounted, T regulatory type 1 (Tr1) cells specific for common environmental allergens consistently represent the dominant subset in healthy individuals. Exposure to high doses of allergens leads to a high concentration of specific IgG(4), detectable IgE and a Tr1 type of immune response. Induction of IL-10- and TGF-beta-producing Tr1 cells, IgG(4) isotype blocking antibodies, and suppressed mast cells, basophils and eosinophils represent major components of a relatively normalized immune response after allergen-specific immunotherapy (SIT).