An investigation of the gut microbiota in patients with NMO revealed the overrepresentation of Clostridium perfringens, and the C. perfringens adenosine triphosphate-binding cassette transporter (ABC), shared a homologous sequence with AQP4 that could cross-react with T cells from patients with NMO (90, 91). Here, AQP4 is linked to neuromyelitis optica.