This study aimed to compare the proportions of circulating follicular helper T (Tfh) and B cell subsets, as well as serum levels of cytokines and chemokines, between patients with neuromyelitis optica spectrum disorder (NMOSD) who are anti-aquaporin-4 antibody (AQP4-ab)–positive and healthy controls, and to investigate the interaction mechanisms between Tfh and B cells. This evidence concerns the gene AQP4 and neuromyelitis optica.