This project will investigate whether a gene-environment interaction can explain why boys are much more often affected by ASD than girls. This study uses a mouse model to investigate the interaction between immunological prenatal stress, a known predisposing environmental factor, with a mutation in a gene that is linked to ASD risk and whether this interaction is different for both sexes. It is hypothesized that males who are genetically vulnerable to develop ASD are more susceptible to the detrimental effects of prenatal immunological stress than genetically vulnerable girls. Knowledge about this sex-specific gene-environment may offer new avenues of enquiry into ASD, provide unique insights into its neurobiology, and therefore impact a variety of areas in ASD research. Identifying sex-specific interacting risk factors and thereby opening the possibility to decrease the chances of high-risk children for autism of developing the disorder would considerably impact the lives of these children and their families.