Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder characterized by deficits in communication, as well as the presence of restricted and repetitive behaviors. The prevalence of ASD is estimated to be about 1 in 59 children. Abnormal microglial growth and activation has been confirmed in the brain of ASD patients indicating inflammation. However, what stimulates microglia remains unknown. Some of the triggers of microglia could be mediators secreted from mast cells, such as histamine and tryptase. We have previously reported elevated serum levels of the peptides neurotensin (NT) and corticotropin-releasing hormone (CRH) in children with ASD in comparison to healthy controls. Moreover, we have shown that NT stimulates human microglia to secrete the proinflammatory cytokine IL-1β and the chemokines CXCL8, CCL2, and CCL5. Significant evidence indicates that small extracellular vesicles (EVs), also called exosomes, are present in blood and other biological fluids and carry molecules, which protect them from degradation. These molecules are delivered directly to other cell types with the potential to induce or modify a disease. Triggers of microglia could be carried in EVs. Therefore, I am currently investigating the presence or function of EVs in inflammation of the brain and ASD pathogenesis.