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

The Interleukin-2 receptor alpha beta gamma complex (IL-2Rαβγ) is the high-affinity heterotrimeric receptor for the cytokine IL-2, consisting of the alpha (CD25), beta (CD122), and common gamma (CD132) subunits [2, 5]. It is predominantly expressed on activated T cells and constitutively on regulatory T cells (Tregs), where it mediates essential signals for lymphocyte proliferation, survival, and functional differentiation via the JAK-STAT, PI3K, and MAPK pathways [3, 12]. In therapeutic contexts, this complex is a double-edged sword; its activation is harnessed in cancer immunotherapy to expand effector T cells and NK cells, while its inhibition is used in autoimmunity and transplantation to suppress unwanted T cell responses [4, 11, 14]. Drugs like aldesleukin (recombinant IL-2) act as agonists to boost immune activity against tumors, but their use is often limited by the expansion of immunosuppressive Tregs and severe side effects such as vascular leak syndrome [6, 14]. Monoclonal antibodies like basiliximab and daclizumab target the CD25 subunit to prevent the assembly of the high-affinity complex, effectively inhibiting the T cell-driven rejection of transplanted organs [11]. Modern drug development focuses on "biased" IL-2 variants that selectively target the dimeric IL-2Rβγ form to avoid Treg expansion or low-dose IL-2 to specifically favor Tregs in autoimmune conditions [4, 10]. The complex's role in immune homeostasis is further highlighted by the fact that mutations in the gamma chain lead to X-linked severe combined immunodeficiency (XSCID) [12]. Overall, the IL-2Rαβγ complex remains a cornerstone of immunomodulatory therapy due to its central role in T cell biology [18].

Other names

High-affinity interleukin-2 receptorCD25/CD122/CD132 complexIL-2R heterotrimerTac/p75/p64 complex

Agonists bind to the heterotrimeric complex to induce conformational changes that activate JAK1 and JAK3, leading to STAT5 phosphorylation and the transcription of genes for T cell growth [3, 4]. Antagonists, typically monoclonal antibodies against the alpha subunit (CD25), competitively inhibit IL-2 binding or prevent the assembly of the high-affinity trimer, thereby suppressing T cell-mediated immune responses [11, 15].