However, it is often unknown to what extent these antibodies are the direct cause for induction of symptoms.42 In myastenia gravis, autoantibodies have a clear disease-causing effect by attacking the acetylcholine receptor,43 whereas in neuromyelitis optica, specific T-cell reactivity is thought to be required for the disease development, in addition to antibodies to aquaporin-4.44, 45 Accordingly, putative autoantibodies may be markers for a more general immune reaction rather than representing specific disease-causing agents. The gene discussed is AQP4; the disease is neuromyelitis optica.