Background：CD56 is a single transmembrane glycoprotein also known as NCAM （neural cell adhesion molecule）, Leu-19, or NKH1. It is a member of the Ig superfamily. The 140 kD isoform is expressed on NK and NKT cells. CD56 is also expressed in the brain （cerebellum and cortex） and at neuromuscular junctions. Certain large granular lymphocyte （LGL） leukemias, small-cell lung carcinomas, neuronal derived tumors, myelomas, and myeloid leukemias also express CD56. CD56 plays a role in homophilic and heterophilic adhesion via binding to itself or heparan sulfate.
