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

Interleukin-2 receptor subunit alpha (CD25) is a type I transmembrane glycoprotein that functions as the alpha chain of the high-affinity IL-2 receptor complex. While CD25 itself has low affinity for IL-2 and no signaling capacity, its association with the beta (CD122) and gamma (CD132) chains creates a high-affinity receptor essential for T-cell expansion and survival (UniProt: P01589). CD25 is constitutively expressed on regulatory T-cells (Tregs) and rapidly upregulated on effector T-cells following antigenic stimulation, making it a hallmark of T-cell activation (PubMed: 25712241). In therapeutic contexts, CD25 is targeted to suppress unwanted immune responses, such as those occurring in organ transplantation or autoimmune diseases like multiple sclerosis (DrugBank: DB00074). Monoclonal antibodies like basiliximab block the IL-2 binding site on CD25, effectively preventing the proliferation of activated T-cells that drive graft rejection (StatPearls: NBK541073). Additionally, CD25 serves as a target for antibody-drug conjugates and immunotoxins in the treatment of certain hematologic malignancies where the protein is overexpressed (PubMed: 31533831).

Other names

IL2RAInterleukin-2 receptor alpha chainTAC antigenp55T-cell activation antigen CD25

Drugs targeting CD25 primarily act as competitive antagonists that bind to the alpha subunit of the IL-2 receptor, preventing the assembly of the high-affinity heterotrimeric complex and blocking IL-2-induced signal transduction and T-cell proliferation (StatPearls: NBK541073). In oncology, CD25-directed agents may also utilize antibody-dependent cellular cytotoxicity (ADCC) or deliver cytotoxic payloads directly to CD25-expressing malignant cells (PubMed: 31533831).