ENPP3 （CD203c, ENPP3） is a member of the human NPP （Nucleotide Pyrophosphatase/Phosphodiesterase） family. It is expressed in various organs, including on epithelial and mucosal surfaces, and is particularly notable on basophils and mast cells. NPP3 serves as a common marker for diagnosing allergen sensitivity by analyzing patient basophils using flow cytometry.
Basophils and mast cells play a role in mediating responses to certain pathogens as well as acute and chronic allergic reactions. Upon activation, these cells release ATP, which further stimulates them in an autocrine manner. The upregulation of NPP3 helps to degrade ATP and suppresses chronic allergic inflammation, without affecting the acute response.