Maternal immune activation imprints a regulatory T cell deficiency in offspring that drives an autism-like phenotype

Abstract Maternal immune activation (MIA) triggers an IL-17-driven autism spectrum disorder (ASD) in mouse and human offspring. While regulatory T cells (Tregs) regulate Th17 cells, their involvement in MIA and ASD pathogenesis is unknown. At the maternal level, we show that Treg stimulation suppresses interleukin-17 (IL-17) production and prevents ASD-like behaviors in offspring. At the offspring level, we show that MIA imprints a systemic and brain Treg deficiency, as evidenced by alterations in the methylome, transcriptome, and functional assays. This deficiency promotes brain inflammation, characterized by infiltration of IL-17–producing cells and neutrophils into the meninges and alterations in cortical brain structure. Stimulation of offspring Tregs with interleukin-2 reversed brain inflammation and cured established ASD-like behaviors. Thus, MIA-induced ASD is a neuroimmune disorder that can be reversed by immunomodulation. One sentence abstract Maternal immune activation during pregnancy imprints a Treg deficiency in offspring that perpetuates brain inflammation and an autism-like phenotype, which can be reversed by Treg stimulation.