CD177 is also known as neutrophil specific antigen 1, NB1, and polycythemia rubra vera 1. It is a member of the uPAR family and is a GPI-linked cell surface glycoprotein with a molecular weight of 60 kD. CD177 is expressed on granulocytes and bone marrow progenitors (early erythroblasts, megakaryocytes). It is thought to be involved in allogeneic and autoimmune responses to neutrophils.