The MaxDiscovery™ Rat GM-CSF ELISA Test Kit is designed for quantitative determination of the concentration of rat GM-CSF in serum, plasma, and cell culture supernatant. Rat mature granulocyte macrophage colony stimulating factor (GM-CSF) is a polypeptide of 127 amino acids with one potential N-linked glycosylation site and two intramolecular disulfide bonds. Natural rat GM-CSF is a monomeric glycoprotein with an apparent molecular mass ranging from 27 - 44 kDa. Rat GM-CSF shares 69% and 62% amino acid sequence identity with mouse and human GM-CSF, respectively. While rat and mouse GM-CSF have reciprocal cross-species activity, they are not active on human cells. GM-CSF is produced by a number of type II alveolar cells, renal mesangial cells, and endothelial cells. It is a pleiotrophic cytokine that stimulates the proliferation, differentiation, migration and survival of hematopoietic progenitor cells of the neutrophil, eosinophil, macrophage, megakaryocyte and erythroid lineages. GM-CSF activates the effector functions of mature neutrophils, eosinophils and macrophages. In concert with IL-4 and other cytokines, GM-CSF induces dendritic cell formation and stimulates their ability to present antigens to cells of the immune system. In addition, GM-CSF inhibits Langerhans cell IL-12 production, thus promoting a generalized Th2-type response. Rat GM-CSF shares 69% and 62% amino acid sequence identity with mouse and human GM-CSF, respectively. While rat and mouse GM-CSFs have reciprocal cross-species activity, they are not active on human cells. Normal mouse and rat sera GM-CSF is undetectable (less than 15.6 pg/mL) in the absence of underlying pathology. In mice and humans, the high-affinity receptor for GM-CSF is composed of a 50 kDa ligand binding alpha subunit (GMR) and a 120 kDa signal transducing beta subunit. Furthermore, syndecan-2 is also reported to be a co-receptor for GM-CSF.