Cytokine secreted predominantly by activated T-lymphocytes as well as mast cells and osteoblastic cells that controls the production and differentiation of hematopoietic progenitor cells into lineage- restricted cells (PubMed:2556442). Also stimulates mature basophils, eosinophils, and monocytes to become functionally activated (PubMed:10779277, PubMed:32889153). In addition, plays an important role in neural cell proliferation and survival (PubMed:23226269). Participates as well in bone homeostasis and inhibits osteoclast differentiation by preventing NF-kappa-B nuclear translocation and activation (PubMed:12816992). Mechanistically, exerts its biological effects through a receptor composed of IL3RA subunit and a signal transducing subunit IL3RB (PubMed:29374162). Receptor stimulation results in the rapid activation of JAK2 kinase activity leading to STAT5-mediated transcriptional program (By similarity). Alternatively, contributes to cell survival under oxidative stress in non- hematopoietic systems by activating pathways mediated by PI3K/AKT and ERK (PubMed:27862234). {ECO:0000250|UniProtKB:P01586, ECO:0000269|PubMed:10779277, ECO:0000269|PubMed:12816992, ECO:0000269|PubMed:23226269, ECO:0000269|PubMed:2556442, ECO:0000269|PubMed:27862234, ECO:0000269|PubMed:29374162, ECO:0000269|PubMed:32889153}. This is the function of IL3 (interleukin 3, ENSG00000164399).