Pediatric neuropsychiatric and movement disorders affect millions of children each year with devastating consequences on families. Work done over the past 12+ years has focused on understanding how infections and autoantibody responses affect the brain. The investigators have found that neuropsychiatric and movement disorders such as pediatric autoimmune neuropsychiatric disorder associated with streptococci (PANDAS) are associated with a group of autoantibodies which may be elevated during disease symptoms and may signal neuronal cells in the brain. This project explores the hypothesis that autism spectrum disorders (ASD) are associated in some instances with PANDAS symptoms where the two diseases may be co-morbid. ASDs are characterized by deficits in social communication and restrictive and repetitive interests and behaviors, and many children with ASD also have intellectual and developmental disabilities. Children diagnosed with ASD can exhibit symptoms associated with other childhood neuropsychiatric disorders such as ADHD, OCD and depression. Specific aims of this proposal include: evaluating and confirming an existing sample of 47 children with autism who demonstrated an acute onset of OCD and/or tic symptoms associated with PANDAS; careful characterization of a general sample of 20-40 children with a firm diagnosis of ASD; and analyzing sera from these children to be analyzed for autoantibodies against neuronal antigens tubulin, lysoganglioside, and D1 and D2 dopamine receptors. Autism sera (IgG) also will be examined for signaling of human neuronal cells in culture. This project will study receptors on neuronal cells and on receptor transfected cells which may be signaled by autoantibodies in autistic sera and provoke altered behaviors in autism. This research has the potential to identify patients with autism who would benefit from immunotherapies or other PANDAS treatments.