Altered phenotype and gene expression of regulatory T cells (Tregs) in children with Autism, and the relationship with comorbid gastrointestinal symptoms

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterized by social deficits and stereotypic behaviors. In ASD, increased numbers of inflammatory cells and their mediators have been found in peripheral blood, brain, and gastrointestinal (GI) tissues. Regulatory T cells (Tregs) play a crucial role in suppressing inflammatory processes that, if disrupted, can result in inflammation and development of a variety of immunological conditions. In this study, we sought to characterize Tregs populations using flow cytometric and gene transcriptomic approaches in children with ASD (n = 36) and typically developing (TD) children (n = 18) enrolled in the Childhood Autism Risk from Genetics and Environment (CHARGE)-back study. We also examined differences in the frequencies of activated Tregs in ASD groups when stratified by stable co-occurring GI status. The frequency of gut homing α4β7+Tregs positive for inhibitory receptors GITR, LAP, and/or GARP were altered based on the presence of GI symptoms. Analysis of mRNA isolated from CD4+CD25+Tregs, showed 213 differentially expressed genes (DEGs) between the ASD and TD children. Upregulated DEGs were enriched in Gene Ontology (GO) Biological Processes involved in epigenetic regulation including ‘chromatin organization’, whereas Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were involved in metabolism, including ‘lipid and atherosclerosis’ and ‘pantothenate and CoA biosynthesis’. Upregulation of immune signaling genes (MAPK3, JAK2, and CASP3) was also noted in ASD Tregs. Downregulated DEGs consisted of genes enriched in immune terms including the GO term ‘leukocyte differentiation’ and KEGG pathways ‘Parkinson disease’ and ‘protein processing in endoplasmic reticulum’. Behavioral correlation analysis pointed to a potential relationship between inappropriate speech scores and lower frequencies of Tregs. Overall, these data support the hypothesis of altered Tregs cell biology in ASD that ultimately may drive a lack of control of inflammatory immune responses in ASD shifting from a balanced state to a dysregulated/inflammatory state.