interleukine2

Interleukin-2 (IL-2; also written interleukine-2 in some texts) is a small secreted cytokine of the interleukin-2 family that plays a central role in the regulation of the immune system. It is produced mainly by activated CD4+ T helper cells in response to antigenic stimulation, with lower amounts produced by other immune cells. IL-2 promotes the growth, differentiation, and survival of T lymphocytes and supports natural killer (NK) cell activity. It acts in autocrine and paracrine fashion to expand antigen-activated T cells during immune responses.

The biological effects of IL-2 are mediated by the IL-2 receptor, which exists in three forms depending on subunit composition: a low-affinity dimer, an intermediate-affinity trimer, and a high-affinity trimer comprising IL-2R alpha (CD25), IL-2R beta (CD122), and the common gamma chain (CD132). High-affinity signaling occurs via JAK-STAT pathways, notably STAT5, after IL-2 binding.

Physiologically, IL-2 is essential for clonal expansion of effector T cells and for the development and maintenance of regulatory T cells, which help restrain immune responses and maintain tolerance.

Clinically, recombinant human IL-2 (aldesleukin) has been used as immunotherapy for certain cancers, including metastatic renal cell carcinoma and malignant melanoma. High-dose IL-2 therapy can elicit durable responses in a subset of patients but is associated with significant toxicity, such as capillary leak syndrome and hypotension, and is typically administered in specialized centers. Low-dose IL-2 regimens are under investigation to expand regulatory T cells in autoimmune and transplantation contexts.