A method of diagnosis, prognosis or treatment of an autoimmune disease in a subject wherein the method comprises detecting aquaporin-1 (AQP1), aquaporin-2 (AQP2), aquaporin-5 (AQP5), aquaporin-7 (AQP7) and/or aquaporin-8 (AQP8) autoantibodies in a sample obtained from said subject.