The transcription factor XBP1 in dendritic cells promotes the T H 2 cell response in airway allergy.

Dendritic cells (DCs) that express T cell immunoglobulin domain molecule-4 (TIM4), a cell surface receptor for phosphatidylserine, induce T helper 2 (T2) cell responses and allergic reactions. We elucidated the role of the transcription factor X-box-binding protein-1 (XBP1) in the induction of the T2 cell response through its role in generating TIM4 DCs. We found that XBP1 was required for TIM4 mRNA and protein expression in airway DCs in response to the cytokine interleukin-2 (IL-2) and that this pathway was required for TIM4 expression on DCs in response to the allergens PM2.5 and Derf1. The IL-2-XBP1-TIM4 axis in DCs contributed to Derf1/PM2.5-induced, aberrant T2 cell responses in vivo. An interaction between the guanine nucleotide exchange factor Son of sevenless-1 (SOS1) and the GTPase RAS promoted XBP1 and TIM4 production in DCs. Targeting the XBP1-TIM4 pathway in DCs prevented or alleviated experimental airway allergy. Together, these data suggest that XBP1 is required for T2 cell responses by inducing the development of TIM4 DCs, which depends on the IL-2-XBP1-SOS1 axis. This signaling pathway provides potential therapeutic targets for the treatment of T2 cell-dependent inflammation or allergic diseases.