Characterization of CD4+ T cell subsets in allergy.

Allergen specific T(H)2 cells are a key component of allergic disease, but their characterization has been hindered by technical limitations and lack of epitope data. Knowledge about the factors that drive the differentiation of naïve T cells into allergy-promoting T(H)2 cells and the influence of allergen specific immunotherapy on the phenotype and function of allergen-specific T cells have also been limited. Recent advances indicate that innate and adaptive immune factors drive the development of diverse subsets of allergen-specific T cells. While allergen-specific T cells are present even in non-allergic subjects, highly differentiated T(H)2 cells are present only in allergic subjects and their disappearance correlates with successful immunotherapy. Therefore, elimination of pathogenic T(H)2 cells is an essential step in tolerance induction.