CD10 is a 100 kD neutral endopeptidase and a member of the metalloprotease family. It is a type II transmembrane protein also known as common acute lymphoblastic leukemia antigen (CALLA), enkephalinase, and neprilysin. CD10 is expressed on B cell precursors, T cell precursors, and neutrophils. CD10 is involved in B cell development and has been shown to bind opioid enkephalins, bradykinin, angiotensins I and II, and other biologically active peptides.