CD177 (NB1, HNA-2a and PRV-1 form) is a GPI-anchored glycoprotein present mainly on neutrophils. Its plasma membrane expression is increased during pregnancy and and inflammation or after G-CSF application. Ligand of CD177 has been identified as CD31 (PECAM-1). CD177 participates in neutrophil transmigration and seems to be also a pro-proliferative molecule. The antibodies against CD177 can be involved in neonatal alloimmune neutropenia (NAN).