Interleukin-2 receptor alpha-beta-gamma high-affinity complex (IL-2Rαβγ)

The Interleukin-2 receptor (IL-2R) alpha-beta-gamma high-affinity complex is a heterotrimeric signaling assembly essential for the regulation of the adaptive immune system (Liao et al., 2013). It consists of three distinct subunits: the alpha chain (CD25), the beta chain (CD122), and the common cytokine receptor gamma chain (CD132) (UniProt, 2024). While the beta and gamma subunits can form an intermediate-affinity receptor, the addition of the alpha subunit creates a high-affinity site that allows cells to respond to very low concentrations of IL-2 (Malek, 2008). This complex is predominantly expressed on activated T cells and regulatory T cells (Tregs), where its activation triggers the JAK/STAT, PI3K/Akt, and MAPK signaling pathways to drive cell proliferation and survival (StatPearls, 2023). In clinical practice, this receptor complex is a major therapeutic target; agonists like Aldesleukin are used to stimulate immune responses in cancer, whereas antagonists like Basiliximab are used to prevent acute organ rejection (FDA, 2023). Furthermore, dysregulation of the high-affinity IL-2R is implicated in various autoimmune disorders and hematologic malignancies, making it a focal point for the development of next-generation immunotherapies (Waldmann, 2006).

Other names

High-affinity IL-2 receptorIL-2R alpha/beta/gammaCD25/CD122/CD132 complexTrimeric IL-2 receptorIL-2Rαβγ

The binding of Interleukin-2 (IL-2) to the high-affinity trimeric receptor complex induces the dimerization of the cytoplasmic domains of the beta (CD122) and gamma (CD132) subunits (Liao et al., 2013). This proximity allows for the cross-phosphorylation and activation of Janus kinases, specifically JAK1 and JAK3 (UniProt, 2024). These kinases then phosphorylate specific tyrosine residues on the receptor's cytoplasmic tail, creating docking sites for STAT5 proteins. Once phosphorylated, STAT5 proteins dimerize and translocate to the nucleus to initiate the transcription of genes essential for T-cell cycle progression and survival (Malek, 2008). Therapeutic antagonists, such as monoclonal antibodies against CD25, work by sterically blocking the IL-2 binding site, thereby preventing the assembly of the high-affinity complex and subsequent downstream signaling (StatPearls, 2023).