This project explores the role of folate receptor (FR) autoantibodies in the pathogenesis of autism. This novel hypothesis is based on preliminary data generated by numerous studies that have reinforced the role of folate as an essential nutrient and folate receptor as the protein necessary for delivering this nutrient to the developing embryo as well as the brain. Identification of low cerebrospinal fluid folate and the presence of FR autoantibodies in children with neurodevelopmental disorders such as cerebral folate deficiency syndrome and autism provide compelling evidence to implicate FR autoimmunity in the developmental deficits. This study encompasses many of the targeted priorities of Autism Speaks in identifying FR autoantibodies as a risk factor for autism and folinic acid administration as a possible treatment to correct the deficit. This research covers epigenetic mechanisms, early detection, novel treatment approaches and dissemination of validated methods. Patients with cerebral folate deficiency that have FR autoantibodies have shown marked improvement in their condition following treatment with folinic acid. Identification of FR autoantibodies in parents will allow us to determine a genetic link and embryonic exposure to FR autoantibodies contributing to the pathology. This study has the potential to provide a method for early detection of autism risk and intervention. The studies are designed to extend preliminary observations on the association of folate receptor autoantibodies with ASD and identify potential mechanism contributing to their pathology.