S100A9/MRP14 [47-8D3]

S100A9, or MRP14, is a member of the S100 family of proteins containing two EF-hand calcium-binding motifs. It forms a heterodimer, Calprotectin, with S100A8 in a calcium-dependent manner. S100A9 may function in the inhibition of casein kinase, and altered expression of this protein is associated with the disease cystic fibrosis. S100A9 is expressed in granulocytes, monocytes in peripheral blood and in infiltrating macrophages in inflammatory sites, but not in normal tissue macrophages. Elevated plasma levels of S100A9 have been observed in inflammatory disorders such as chronic bronchitis, cystic fibrosis and rheumatoid arthritis. S100A9 is also detected in tumor cells in carcinomas of the liver, lung, breast and thyroid. The expression of S100A9 is correlated with tumor differentiation.