Basophils Function as Antigen Presenting Cells for an Allergen-Induced T(H)2 Response

T(H)2 mediated immune responses are induced upon infection with multicellular parasites and can be triggered by a variety of allergens. Mechanisms of induction and the antigen-presenting cells involved in activation of T(H)2 responses remain poorly defined and the innate immune sensing pathways activated by parasites and allergens are largely unknown. Basophils are required for the in vivo induction of T(H)2 responses by protease allergens. Here we show that basophils also function as antigen presenting cells. We show that, while dendritic cells were dispensable, antigen presentation by basophils was necessary and sufficient for allergen-induced activation of T(H)2 responses in vitro and in vivo. Thus, basophils function as antigen presenting cells for T(H)2 differentiation in response to protease allergens.