Altered Microbiota-GALT Communication in IBD and ASD: Changes in IELs and AhR/ARNT Gene Polymorphism

Growing recognition of the microbiota and gut-associated lymphoid tissue (GALT) as a significant component of human health calls for a better understanding of the mechanisms involved in the host-microbiota interactions. The communication between the microbiota in the external milieu of the gut lumen and the host across the gastrointestinal barrier (GIB) involves recognition, selective response to the commensal vs. the pathogenic microorganisms and antigens, and adaptation, and is orchestrated by the GALT. In health, GALT assures GIB integrity and microbiota symbiosis; in disease, altered GALT's functions compromise GIB integrity and lead to dysbiosis associated with gastrointestinal immune    pathologies such as inflammatory bowel diseases (IBD) and neurodevelopmental disorders such as autism spectrum disorder (ASD). These pathologies are often accompanied by a "leaky gut syndrome" defined as increased intestinal permeability to pathogens. This review focuses on the microbiota-GALT communication involving intraepithelial lymphocytes (IELs) and their aryl hydrocarbon receptors (AhRs). It posits that changes in the IELs or their aryl hydrocarbon receptor (AhRs) jeopardizes GIB integrity and contribute to pathologies such as IBD and ASD. Hence, AhRs activity is regulated by the antiinflammatory dietary ligands present in cruciferous vegetables and fruits, further research is warranted into diet-derived immunotherapies targeting both gastrointestinal immune and neurodevelopmental disorders.