Both cell-based biopanning (using AQP4-expressing mammalian cells) and FACS screening (using solubilized AQP4 antigen) were effective at enriching AQP4-binding clones, and the screening parameters established in this study will help us to effectively screen large antibody libraries, which will help us better understand the antibody response in NMO and other autoimmune patients. The gene discussed is AQP4; the disease is neuromyelitis optica.