IL2 (interleukin-2) is a cytokine produced primarily by activated CD4+ helper T cells and, to a lesser extent, by CD8+ T cells and natural killer cells 1. It functions as a critical regulator of immune responses through binding to high-affinity trimeric or low-affinity dimeric IL-2 receptor complexes, triggering JAK1/JAK3 phosphorylation and downstream STAT5, PI3K, and MAPK pathway activation 234. IL2 acts as a T-cell growth factor, promotes NK-cell cytolytic activity, and drives B-cell proliferation and immunoglobulin production 51. Functionally, IL2 regulates regulatory T-cell survival and proliferation essential for immune tolerance, while controlling effector T-cell differentiation and memory responses 6. Its pleiotropic nature presents both opportunities and challenges: IL2-based immunotherapies have achieved durable responses in metastatic melanoma and renal cancer 7, and targeted IL2 delivery to CD8+ T cells shows promise for cancer immunotherapy and chr4 viral infections like hepatitis B 89. However, IL2's broad receptor distribution on Tregs and NK cells can limit efficacy and cause toxicity, driving development of engineered variants with selective targeting 1011. IL2 gene polymorphisms have also been associated with periodontitis susceptibility 12.