Interleukin-2 receptor, high-affinity trimeric complex (IL-2R)

The Interleukin-2 receptor (IL-2R) high-affinity trimeric complex is a critical mediator of the adaptive immune system, consisting of three distinct subunits: IL-2Rα (CD25), IL-2Rβ (CD122), and the common gamma chain (γc, CD132) [1, 5]. This complex is primarily expressed on activated T cells and regulatory T cells (Tregs), where it binds the cytokine IL-2 with exceptionally high affinity to initiate signaling through the JAK-STAT pathway, particularly involving JAK1, JAK3, and STAT5 [2, 13]. Its biological role is dualistic; it promotes the expansion of effector T cells and natural killer (NK) cells to combat pathogens and tumors, while also maintaining Treg populations to ensure self-tolerance and prevent autoimmunity [14, 15]. In clinical practice, the receptor is a major therapeutic target: IL-2R antagonists like basiliximab are used to prevent organ transplant rejection by blocking T-cell activation, whereas IL-2 agonists like aldesleukin are employed in cancer immunotherapy to stimulate anti-tumor responses [1, 11]. Dysregulation of this receptor complex is linked to various conditions, including hematologic malignancies, autoimmune disorders like systemic lupus erythematosus, and graft-versus-host disease [2, 11]. Monitoring soluble IL-2R (sIL-2R) levels serves as a valuable clinical biomarker for assessing systemic immune activation and disease progression [8, 10].

Other names

CD25/CD122/CD132 complexHigh-affinity IL-2 receptorIL-2R alpha/beta/gamma complexTac antigen/CD122/CD132Interleukin-2 receptor alpha/beta/gamma

Competitive antagonism of IL-2 binding to the alpha subunit (CD25) to prevent T-cell activation; Agonism of the trimeric receptor complex to trigger JAK1/JAK3 and STAT5 signaling for immune stimulation.