GAD2 and Autoimmunity: Measurements of GAD65-Abs in cerebrospinal fluid (CSF) and serum, as well as analysis of intrathecal synthesis were proposed to be important to identify GAD associated autoimmunity (16), Based on the dynamic turnover rate of immunoglobulin G (IgG) between serum and CSF, around 1% of the serum levels of these antibodies would enter the CSF (18, 22).