The MaxDiscovery™ Human IL-3 ELISA Test Kit is designed for quantitative determination of the concentration of human IL-3 in serum, plasma, and cell culture supernatant. Human interleukin 3 (IL-3) is a glycoprotein of 133 amino acids after cleavage of a 19 amino acid signal sequence. It is a pleiotropic factor that can stimulate the proliferation, differentiation, and survival of pluripotent hematopoietic stem cells as well as various lineage-committed progenitors. IL-3 is produced by several cell types including activated human T cells, natural killer cells, mast cells, epithelial cells, stromal cells, keratinocytes, neuronsand astrocytes. At the amino acid level, there is only 29% homology between mouse and human IL-3. Consistent with this lack of homology, the proteins are species-specific in their actions. IL-3 exerts its biological activities through binding to heteromeric transmembrane receptors. It has been shown that IL-3 alone, or acting synergistically with other early acting hematopoietic growth factors including, IL-1, IL-6, stem cell factor, G-CSF, MGDF, and Flt-3 ligand, can support the proliferation of pluripotent hematopoietic stem cells and progenitor cells of various lineages. In addition to its effects on hematopoietic cells, IL-3 can stimulate human endothelial and smooth muscle cell proliferation and motility and can act as a neurotrophic factor with the ability to promote neuronal survival and enhance neurite outgrowth. IL-3-/- mice do appear to exhibit deficiencies in mast cell and basophil development in addition to compromised immunity to parasites and reductions in delayed hypersensitivity reactions.