Since we previously found associations between antibacterial antibodies and IgG natural autoantibodies in various autoimmune diseases [22, 23] and several infections, including Chlamydia pneumoniae, Chlamydia trachomatis, Mycoplasma pneumoniae, Helicobacter pylori, and Borrelia burgdorferi [26], are reported to have a potential role in the development of NMOSD or MS, we measured IgM, IgG, and IgA antibodies directed against these pathogens. Here, CD40LG is linked to infection.