Interleukin-3 (IL-3) is a potent growth promoting cytokine. IL-3 can stimulate the proliferation and differentiation of pluripotent hematopoietic stem cells as well as various lineage committed progenitors. IL-3 exerts its biological function through binding to specific cell surface receptors. The amino acid sequences of this protein among different species share relatively low identity and its activity is highly species-specific. IL-3 has also been shown to possess neurotrophic activity, and is thought to be associated with neurologic disorders.