TRAF4 is crucial for ST2(+) memory Th2 cell expansion in IL-33–driven airway inflammation

Tumor necrosis factor receptor–associated factor 4 (TRAF4) is an important regulator of type 2 responses in the airway; however, the underlying cellular and molecular mechanisms remain elusive. Herein, we generated T cell–specific TRAF4-deficient (CD4-cre Traf4(fl/fl)) mice and investigated the role of TRAF4 in memory Th2 cells expressing IL-33 receptor (ST2, suppression of tumorigenicity 2) (ST2(+) mTh2 cells) in IL-33–mediated type 2 airway inflammation. We found that in vitro–polarized TRAF4-deficient (CD4-cre Traf4(fl/fl)) ST2(+) mTh2 cells exhibited decreased IL-33–induced proliferation as compared with TRAF4-sufficient (Traf4(fl/fl)) cells. Moreover, CD4-cre Traf4(fl/fl) mice showed less ST2(+) mTh2 cell proliferation and eosinophilic infiltration in the lungs than Traf4(fl/fl) mice in the preclinical models of IL-33–mediated type 2 airway inflammation. Mechanistically, we discovered that TRAF4 was required for the activation of AKT/mTOR and ERK1/2 signaling pathways as well as the expression of transcription factor Myc and nutrient transporters (Slc2a1, Slc7a1, and Slc7a5), signature genes involved in T cell growth and proliferation, in ST2(+) mTh2 cells stimulated by IL-33. Taken together, the current study reveals a role of TRAF4 in ST2(+) mTh2 cells in IL-33–mediated type 2 pulmonary inflammation, opening up avenues for the development of new therapeutic strategies.