In this study, blood cell counts and serum C3, C4, and CH50 values at baseline and after more than 6-month drug use were measured to elucidate changes in blood cells and complements during relapse prevention therapies for aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4+ NMOSD). The gene discussed is AQP4; the disease is neuromyelitis optica.