IRF3 (Interferon Regulatory Factor 3) is a crucial transcription factor in the IRF family, playing a central role in innate immunity, particularly in antiviral responses. Upon viral invasion, pattern recognition receptors (e.g., TLR3, RIG-I) recognize viral components and, through adaptor proteins (TRIF, MAVS), activate the kinases TBK1/IKK蔚, leading to phosphorylation of the C-terminal domain of IRF3. This results in the formation of IRF3 homodimers, which translocate to the nucleus. In the nucleus, IRF3 cooperates with transcription factors such as NF-魏B to activate the expression of type I interferons (IFN-伪/尾) and pro-inflammatory cytokines, initiating a broad-spectrum antiviral state. Additionally, IRF3 can induce apoptosis in infected cells to limit viral spread. Its activity is regulated by viral evasion mechanisms (e.g., HCV cleavage of MAVS), and its dysregulation is associated with autoimmune diseases and cancer pathology.