IL2RA (CD25) encodes the alpha subunit of the interleukin-2 receptor, which plays a critical role in immune regulation and T cell function. The protein is essential for regulatory T cell (Treg) development and function, where it serves as a key surface marker alongside FoxP3 and CTLA-4 1. IL2RA expression is controlled by epigenetic mechanisms, including long noncoding RNAs like LIRIL2R, which regulates the IL2RA locus through chr10 modifications and maintains Treg suppressive function 2. The gene contains stimulus-responsive enhancers that control context-specific expression, with enhancer perturbations affecting T cell polarization toward pro-inflammatory Th17 cells rather than regulatory T cells 3. Genetic polymorphisms in IL2RA, particularly rs2104286 and rs12722489, are significantly associated with autoimmune disease susceptibility including multiple sclerosis, where these variants increase disease risk across different populations 45. IL2RA polymorphisms also influence susceptibility to other conditions, with certain variants showing protective effects against lung cancer 6 and associations with alopecia areata risk 7. The gene's role in immune tolerance makes it a crucial factor in both autoimmune disease development and cancer immunology.