Interleukin-2 receptor alpha (IL2RA), also known as CD25. is a key component of the high-affinity interleukin-2 (IL-2) receptor complex. IL-2 is a cytokine critical for T-cell proliferation, differentiation, and immune regulation. The IL-2 receptor exists in three forms: low-, intermediate-, and high-affinity, with the high-affinity receptor comprising IL2RA (α-chain), IL2RB (β-chain), and IL2RG (γ-chain). IL2RA is primarily expressed on regulatory T cells (Tregs), activated effector T cells, and some innate immune cells, playing a dual role in promoting immune activation and tolerance.
Antibodies targeting IL2RA have significant research and clinical relevance. In basic research, they are used to study Treg function, IL-2 signaling pathways, and immune homeostasis. Clinically, IL2RA antibodies like daclizumab (a humanized monoclonal antibody) were historically used to modulate immune responses in autoimmune diseases and organ transplantation by blocking IL-2 binding to T cells. However, safety concerns led to their discontinuation. IL2RA is also a biomarker in autoimmune diseases (e.g., type 1 diabetes, multiple sclerosis) and cancers, where its expression correlates with disease activity or prognosis. Current therapeutic strategies explore IL2RA-targeting agents to selectively deplete Tregs in cancer immunotherapy or enhance Treg activity in autoimmunity. Challenges remain in balancing efficacy and toxicity due to IL-2's pleiotropic roles.