Antibody 2D9 recognizes human S100A7 (Psoriasin). S100A7 is a 11.4kDa member of the S100 gene family, which are EF-hand Ca 2+-binding proteins. They are involved in a broad range of intra- and extracellular processes like regulation of calcium homeostasis, cell proliferation, differentiation, apoptosis, immune responses, antimicrobial activity, chemotaxis and inflammation. S100 proteins have a fundamental structural unit which is a highly integrated dimer, some as homodimer and others as heterodimer. S100A7 functions as a homodimer and binds two Zn2+ ions. These ions stabilize the dimer and mediate the function of S100A7 during infection. Extracellular S100A7 functions as a DAMP during infection. S100A7 limits bacterial infection through metal limitation. Furthermore, S100A7interacts with RAGE which drives an NF-B mediated proinflammatory response and recruitment of neutrophils.S100A7was first discovered as a protein abundantly expressed in psoriatic keratinocytes. Possibly, S100A7 adheres directly to and reduces survival of pathogens found on the epidermis and acts as a physical barrier. S100A7 also seems to be involved with breast cancer and squamous cell carcinoma. In vitro it was found to confer a more aggressive behavior