Although there is a strong genetic component to autism and autism spectrum disorder, there are non-genetic causal factors. Maternal viral infection has been put forward as one such factor. During an infection, the immune system releases molecules called cytokines which then trigger an increase in MHC-I molecules. Dr MacAllister's team has previously shown that altered MHC-I levels can affect the brain by reducing the ability of neurons to form synapses and modifying existing connections. Therefore, it is possible that modifications of immune function may alter normal brain development and possibly produce symptoms of ASD. This new research will investigate the specific role of cytokines on MHC-I expression and how these changes affect neuronal development. This will be done by measuring MHC-I levels after administration of cytokines as well as examining the number of synapses following exposure. Finally, the function of these neuronal connections will be tested to determine whether the immune response, possibly altered in autism, leads to impaired connectivity and circuitry. What this means for people with autism: Changes in immune system function have been reported in individuals with autism, but the consequences of this hyperactivity on brain development are not yet well understood. These studies will lead to a better understanding of the neurobiological consequences of altered immune activity, and how they relate to ASD.