Basophils function as antigen-presenting cells for an allergen-induced T helper type 2 response

Abstract

Basophils act as effector cells in immunoglobulin E–mediated hypersensitivity responses. Artis, Nakanishi and Medzhitov and their colleagues report that basophils present antigen and induce T helper type 2 responses to helminths, allergens and immunoglobulin E immune complexes. T helper type 2 (TH2)-mediated immune responses are induced after infection with multicellular parasites and can be triggered by a variety of allergens. The mechanisms of induction and the antigen-presenting cells involved in the activation of TH2 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 TH2 responses by protease allergens. Here we show that basophils also function as antigen-presenting cells. We show that although dendritic cells were dispensable for allergen-induced activation of TH2 responses in vitro and in vivo, antigen presentation by basophils was necessary and sufficient for this. Thus, basophils function as antigen-presenting cells for TH2 differentiation in response to protease allergens.