Besides fighting off infection, the immune system is now known to influence the way brain cells are shaped and sculpted. One immune system mediator of importance in ASD is a chemical called IL6, which is elevated following immune challenges associated with autism risk. This study will examine the role of IL6 in the brain in both an animal model of Rett Syndrome and cells from people with Rett Syndrome. Girls with Rett have several similarities to girls with autism, including the feature of loss of previously acquired skills, or regression. Therefore, understanding how specific genes influence autism risk is important for understanding autism in all forms. This study will more fully characterize the contribution of astrocytes, brain cells that can release IL6, on mutations of MeCP2, and more fully explain the role of immune molecules in neurodevelopmental disorders. This fellowship is being co- funded with the Rett Syndrome Research Foundation.