Interleukin-7 (IL-7)

Interleukin-7 (IL-7) is a cytokine and hematopoietic growth factor primarily secreted by stromal cells in the bone marrow and thymus, but also produced by keratinocytes, follicular dendritic cells, and some epithelial cells. It is essential for immune system development, maintenance, and function, playing a crucial role in the proliferation and survival of lymphoid cells, particularly T-cells. IL-7 signals through the IL-7 receptor, activating the Jak/STAT5 and PI3K/Akt pathways. Recombinant human IL-7 has been tested clinically for immune reconstitution.

IL-7 exerts its effects through binding to the IL-7 receptor (IL-7R), a heterodimer composed of the interleukin 7 receptor alpha chain (IL‑7Rα) and common gamma chain receptor (γc). Upon ligand binding, the associated Janus kinases Jak1 (with IL‑7Rα) and Jak3 (γc) are activated. This triggers phosphorylation cascades activating STAT proteins—primarily STAT5—which translocate to the nucleus to regulate gene expression. The PI3K-Akt pathway is also activated to promote cell cycle progression and glucose metabolism. It also regulates anti-apoptotic and pro-apoptotic proteins for survival.