[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Immunology](https://durgical.com/en/immunology/) › [Cytokines and molecules](https://durgical.com/en/immunology/#a-molecules) › Interleukin-2 [Immunology](https://durgical.com/en/immunology/) · [Cytokines and molecules](https://durgical.com/en/immunology/#a-molecules) # Interleukin-2 - Molecule IL-2 is the growth signal T cells give themselves after they recognise an antigen; regulatory T cells also depend on it. Updated 2026-11-01 ## Key points - Source: activated T cells (mainly CD4); acts on T cells, NK cells and regulatory T cells. - High-affinity receptor: CD25 (α) + CD122 (β) + CD132 (common γ chain); signals through JAK1/JAK3 and STAT5. - CD25 is the marker of regulatory T cells (CD4+ CD25+ FOXP3+). - Common γ chain (IL2RG) defects cause X-linked SCID: no T or NK cells. - Calcineurin inhibitors (cyclosporine, tacrolimus) reduce IL-2 production; basiliximab targets the IL-2 receptor. ## What it is Interleukin-2 is made mainly by activated CD4 T cells and makes T cells divide (clonal expansion). It is just as important for regulatory T cells, which carry the high-affinity IL-2 receptor permanently and need IL-2 to keep FOXP3 switched on. That double role explains why both blocking IL-2 (transplant) and giving it (cancer, research in autoimmunity) are used in medicine. ## Structure - Receptor chains: α (CD25), β (CD122) and the common γ chain (CD132). - The common γ chain is shared with the receptors of IL-4, IL-7, IL-9, IL-15 and IL-21. ## Function - Clonal expansion of antigen-activated T cells. - Activation and growth of NK cells. - Survival and suppressive function of regulatory T cells; Tregs also soak up IL-2 and so limit effector T cells. ## Clinical notes - X-linked severe combined immunodeficiency: variants in IL2RG block the development of T and NK cells and leave B cells non-functional; almost only boys. - Transplant: calcineurin inhibitors block IL-2 gene transcription; basiliximab is used to prevent early kidney-graft rejection. - Aldesleukin (recombinant IL-2) is used in metastatic kidney cancer and melanoma; capillary leak syndrome is its typical serious reaction. - Low-intensity IL-2 to expand regulatory T cells is being studied in autoimmune diseases. ## Memory aid IL-2 is the T cell's own fertiliser, and the Treg is the gardener who keeps most of it. ## Test yourself Think of the answer, then tap the question to see it. ## Which chain of the IL-2 receptor marks regulatory T cells? CD25, the α chain; Tregs are CD4+ CD25+ FOXP3+. ## What disease results from loss of the common γ chain? X-linked severe combined immunodeficiency, with absent T and NK cells and non-functional B cells. ## How do cyclosporine and tacrolimus reduce T-cell activation? They inhibit calcineurin, so the NFAT factor cannot turn on the IL-2 gene and T cells do not expand. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/immunology/interleukin-2/) ## Related - [Cytokines: the table to know](https://durgical.com/en/immunology/cytokines-the-table-to-know/) - [IL-10 and TGF-β (the brakes)](https://durgical.com/en/immunology/il-10-and-tgf/) - [Fc receptors, BCR and TCR](https://durgical.com/en/immunology/fc-receptors-bcr-and-tcr/) - [Regulatory T cell (Treg, FOXP3)](https://durgical.com/en/immunology/regulatory-t-cell/) - [T-cell activation: two signals and superantigens](https://durgical.com/en/immunology/t-cell-activation-two-signals-and-superantigens/) - [T-cell and combined deficiencies: DiGeorge, SCID, Wiskott–Aldrich, ataxia-telangiectasia](https://durgical.com/en/immunology/t-cell-and-combined-deficiencies-digeorge-scid-wiskott-aldrich-ataxia-telangiect/) - [Immunosuppressants by mechanism (classes)](https://durgical.com/en/immunology/immunosuppressants-by-mechanism/) ## In Pharmacology - [Basiliximab](https://durgical.com/en/pharmacology/basiliximab/) - [Calcineurin inhibitors](https://durgical.com/en/pharmacology/classes/calcineurin-inhibitors/) [← All of immunology](https://durgical.com/en/immunology/) Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given. Sources: [Regulation of Treg cells by cytokine signaling and co-stimulatory molecules](https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2024.1387975/full) (Frontiers in Immunology, 2024); [IL2RG gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/il2rg/) (MedlinePlus Genetics (U.S. National Library of Medicine), 2025); [Aldesleukin: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a692009.html) (MedlinePlus (U.S. National Library of Medicine), 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/immunology/interleukin-2/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/interleukin-2/