Immunology · Cytokines and 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
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.
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.
Related
- Cytokines: the table to know
- IL-10 and TGF-β (the brakes)
- Fc receptors, BCR and TCR
- Regulatory T cell (Treg, FOXP3)
- T-cell activation: two signals and superantigens
- T-cell and combined deficiencies: DiGeorge, SCID, Wiskott–Aldrich, ataxia-telangiectasia
- Immunosuppressants by mechanism (classes)
In Pharmacology
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 (Frontiers in Immunology, 2024); IL2RG gene: MedlinePlus Genetics (MedlinePlus Genetics (U.S. National Library of Medicine), 2025); Aldesleukin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025).
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Representative model, for educational purposes only.