Prenatal challenges to the immune system in animals (i.e., maternal immune activation) (68) can also lead to many features like those present in ASD brains. Maternal immune activation leads to increased cellular proliferation, brain size, and ASD-like behaviors in animal models (69–72). Intriguingly, an elevated prevalence of MEIs was observed in a primate model of maternal immune activation (73). Elevated MEI levels likewise are observed in schizophrenia (73) and Rett syndrome patients (74), suggesting that somatic MEI burden may play a role in the etiology of some neurodevelopmental and neuropsychiatric diseases.
