Interleukin-2 receptor (high-affinity trimeric form) (IL-2Rαβγ)

The high-affinity trimeric Interleukin-2 receptor (IL-2R) is a heterotrimeric protein complex composed of the alpha (CD25), beta (CD122), and gamma (CD132) subunits [1][4]. It is primarily expressed on activated T cells and regulatory T cells (Tregs), where it mediates the potent proliferative and survival signals of Interleukin-2 (IL-2) via the JAK/STAT, PI3K/Akt, and MAPK pathways [2][5]. Unlike the dimeric form (beta/gamma), which has intermediate affinity, the trimeric form binds IL-2 with very high affinity (Kd ~10^-11 M), allowing cells to respond to low concentrations of the cytokine [1][2]. This receptor plays a critical role in maintaining immune homeostasis by supporting Treg function and driving the expansion of effector T cells during an immune response [2]. In disease states, over-activation or over-expression of the receptor is associated with autoimmune disorders, graft-versus-host disease, and certain lymphoid malignancies [3][5]. Therapeutically, the trimeric IL-2R is targeted by monoclonal antibodies like basiliximab to prevent organ transplant rejection by blocking the CD25 subunit [5]. Conversely, IL-2 agonists like aldesleukin utilize this receptor to boost the immune response in metastatic melanoma and renal cell carcinoma [3]. However, systemic activation of the high-affinity receptor can lead to severe side effects such as capillary leak syndrome, which has led to the development of alpha-independent IL-2 variants that avoid the trimeric form [3][5]. Monitoring soluble CD25 levels serves as a valuable biomarker for disease activity and treatment response in various inflammatory and neoplastic conditions [6].

Other names

High-affinity IL-2 receptorCD25/CD122/CD132 complexIL-2R-alpha/beta/gammaTrimeric IL-2 receptorIL2R

Drugs targeting the high-affinity IL-2 receptor act as either agonists to stimulate T-cell expansion (e.g., IL-2 analogs) or antagonists to block IL-2 signaling and suppress immune responses (e.g., monoclonal antibodies against the CD25 subunit). [1][3][5]