TRAF3IP3 (TRAF3 interacting protein 3) is an immune adapter protein with complex roles in immunity and cancer. In normal immune function, TRAF3IP3 is essential for B cell development and survival, particularly marginal zone B cells, by promoting autophagy and preventing apoptosis 1. The protein enhances antiviral immunity by inhibiting viral replication, though viruses like EV71 can cleave TRAF3IP3 to escape this antiviral response 2. Mechanistically, TRAF3IP3 functions through multiple pathways including regulation of lysosomal metabolism and autophagy. In regulatory T cells, it facilitates GARP/TGF-β1 complex formation in lysosomes, contributing to immunosuppressive functions 3. In cancer contexts, TRAF3IP3 exhibits tissue-specific dual roles. While it promotes tumor growth and angiogenesis in melanoma 4, it acts as a tumor suppressor in lung adenocarcinoma by inducing ER stress-mediated apoptosis through the PERK/ATF4/CHOP pathway 5. In hepatocellular carcinoma, decreased TRAF3IP3 expression correlates with poor prognosis and reduced immune infiltration 6. These opposing functions highlight TRAF3IP3's context-dependent role as either an oncogene or tumor suppressor, making it a potential therapeutic target requiring tissue-specific approaches.