Interleukin-2 receptor alpha subunit (CD25) (IL-2RA)

The Interleukin-2 receptor alpha subunit (CD25) is a 55 kDa transmembrane glycoprotein that serves as a critical component of the high-affinity heterotrimeric IL-2 receptor complex, alongside the beta (CD122) and gamma (CD132) chains (UniProt P01589). While CD25 lacks an intracellular signaling domain, its expression is essential for increasing the affinity of the receptor for IL-2 by approximately 100-fold, facilitating rapid T-cell expansion and the maintenance of regulatory T cells (Tregs) (StatPearls, Interleukin 2). In healthy individuals, CD25 is constitutively expressed on Tregs but is only transiently expressed on effector T cells following antigen stimulation. This differential expression makes it a valuable therapeutic target for selectively suppressing activated immune responses in organ transplantation and autoimmune diseases like multiple sclerosis (DrugBank, Basiliximab). Furthermore, CD25 is overexpressed in various hematologic malignancies, such as adult T-cell leukemia, making it a target for antibody-drug conjugates and immunotoxins designed to eliminate malignant cells while sparing resting lymphocytes (PubMed, PMC7355333).

Other names

CD25IL2RAT-cell activation antigenTAC antigenp55IDDM10TCGFR

Monoclonal antibodies like basiliximab and daclizumab act as competitive antagonists by binding to the alpha subunit (CD25) of the high-affinity IL-2 receptor complex on activated T cells, thereby preventing IL-2 from binding and inhibiting T-cell proliferation. Other agents, such as denileukin diftitox, utilize the receptor for targeted delivery of cytotoxic toxins to CD25-expressing malignant cells.