IKZF4 (Eos) is a zinc finger transcription factor functioning as a DNA-binding protein that recognizes the GGGAATRCC sequence and acts as a transcriptional repressor 1. It plays essential roles in immune regulation and tumor suppression. In regulatory T cells, IKZF4 mediates FOXP3-dependent gene silencing and is critical for optimal Foxp3 protein expression and Treg cell function 2. IKZF4 operates within the IKZF4/NONO-RAB11FIP3 axis to facilitate PD-L1 endosomal recycling, promoting immune evasion in gastric cancer, while IKZF4 silencing enhances anti-tumor immunity 1. In non-small cell lung cancer, IKZF4 functions as a tumor suppressor by inhibiting Notch signaling 3. Genetically, IKZF4 variants associate with multiple autoimmune diseases: genome-wide association studies identified IKZF4 polymorphisms linked to alopecia areata risk 45, narcolepsy type 1 6, and type 1 diabetes 78. Notably, IKZF4 rs1701704 polymorphism shows sexual dimorphism in type 1 diabetes progression, with protective effects in females 8. These findings establish IKZF4 as a multifunctional regulator bridging adaptive immunity, autoimmunity, and cancer biology.