Homodimeric cytokine expressed predominantly by T-lymphocytes and NK cells that plays an important role in the survival, differentiation, and chemotaxis of eosinophils (PubMed:2653458, PubMed:9010276). Acts also on activated and resting B-cells to induce immunoglobulin production, growth, and differentiation (By similarity). Mechanistically, exerts its biological effects through a receptor composed of IL5RA subunit and the cytokine receptor common subunit beta/CSF2RB (PubMed:1495999, PubMed:22528658). Binding to the receptor leads to activation of various kinases including LYN, SYK and JAK2 and thereby propagates signals through the RAS-MAPK and JAK-STAT5 pathways respectively (PubMed:7613138). Homodimer; disulfide-linked (PubMed:8483502, PubMed:22528658). Interacts with IL5RA (PubMed:1495999, PubMed:22153509). Interacts with CSF2RB (PubMed:1495999). Belongs to the IL-5 family. Interleukin-5 entry