Role of basophils in the initiation of Th2 responses

Abstract

Long appreciated for their role as Type-2 effector cells, basophils have recently come into the spotlight for their role in the initiation of Type-2 immunity. Via an assortment of different activation pathways, basophils produce cytokines such as IL-4 that promote Th2 differentiation. Furthermore, recent studies using different experimental systems have shown that basophils can act as antigen presenting cells both in vitro and in vivo. In addition, basophils shape the Type-2 immune response by guiding antibody production and the memory response.

Figure

Basophils directly influence both T cell differentiation and antibody production by B cells. On the right, a basophil is depicted taking up antigen either via IgE mediated antigen uptake or by endocytosis of soluble antigen (hexagon). After activation stimulus, either activation by a protease allergen or IgE crosslinking, antigen is processed and presented on MHC Class II. Basophils also upregulated costimulatory molecules such as CD40 and secrete cytokines such as IL-4 and TSLP that together activate Th0 cells and induce skewing to the Th2 phenotype. On the left, IgD crosslinking leads to basophil activation, exhibited by upregulation of CD40L and production of IL-4 and BAFF. This results in T independent IgE production from B cells.