IL3

Interleukin-3 (IL-3) is a cytokine that regulates early hematopoiesis in humans. It is produced by activated T cells and, in some settings, by mast cells. IL-3 stimulates survival, proliferation, and differentiation of multipotent hematopoietic progenitors, supporting the development of several myeloid lineages, including erythroid, megakaryocytic, granulocytic, and monocytic cells. In laboratory assays, IL-3 often acts together with GM-CSF to enhance colony formation and lineage commitment.

Receptor and signaling: IL-3 signals through a heterodimeric receptor composed of a private IL-3 receptor alpha chain (IL-3Rα, CD123) and the shared beta common chain (βc, CD131/CSF2RB) used by GM-CSF and IL-5 receptors. Binding activates associated JAK kinases, chiefly JAK2, and downstream pathways such as STAT5 and STAT3, as well as MAPK and PI3K-Akt signaling, leading to transcriptional programs that promote proliferation and survival.

Biological and clinical notes: IL-3 acts broadly on early hematopoiesis and can influence basophil and eosinophil development; it also participates in inflammatory responses. Therapeutically, IL-3 has been explored to accelerate hematopoietic recovery after transplantation, but its broad activity and short half-life limit routine use as a single agent. In hematologic malignancies, components of the IL-3 signaling axis, particularly CD123, can be overexpressed, and CD123-targeted therapies are under development or in use for certain conditions such as blastic plasmacytoid dendritic cell neoplasm and some acute myeloid leukemias.