IL-2 Protein, Human (His)

The cytokine interleukin-2 (IL-2), produced primarily by activated CD4-positive helper T-cells and, to a lesser extent, by activated CD8-positive T-cells and natural killer (NK) cells, plays pivotal roles in the immune response and tolerance. IL-2 binds to a receptor complex composed of either the high-affinity trimeric IL-2R (IL2RA/CD25, IL2RB/CD122, and IL2RG/CD132) or the low-affinity dimeric IL-2R (IL2RB and IL2RG). This interaction induces oligomerization and conformational changes in the IL-2R subunits, initiating downstream signaling with the phosphorylation of JAK1 and JAK3. Subsequently, JAK1 and JAK3 phosphorylate the receptor, creating a docking site for the phosphorylation of various substrates, including STAT5. This process activates multiple pathways, including STAT, phosphoinositide-3-kinase/PI3K, and mitogen-activated protein kinase/MAPK pathways. IL-2 functions as a T-cell growth factor, enhances NK-cell cytolytic activity, and promotes robust proliferation of activated B-cells, leading to increased immunoglobulin production. Furthermore, IL-2 plays a crucial role in regulating the adaptive immune system by controlling the survival and proliferation of regulatory T-cells, essential for maintaining immune tolerance. Additionally, IL-2 participates in the differentiation and homeostasis of various effector T-cell subsets, including Th1, Th2, Th17, as well as memory CD8-positive T-cells.