Decreased Immune Regulation in Children with ASD Who Experience GI Symptoms

Background: Multiple studies have reported increased prevalence of gastrointestinal (GI) symptoms in children with autism spectrum disorders (ASD) and one recent study estimated that children with ASD are 6 to 8 times more likely to have persistent GI symptoms including: diarrhea, constipation, alternating bowel habits, gassiness or bloating, vomiting and abdominal pain have been reported in numerous studies. In addition, intestinal and peripheral inflammation, altered microbiome profiles, and impaired intestinal permeability have been observed in children with ASD who experience GI symptoms.

Objectives: To assess immune dysfunction and relationship to behavior in children with ASD with and without GI co-morbidities.

Methods: Over a hundred children participated in our study and were placed into one of four study groups based on responses from two questionnaires: children with ASD who experience GI symptoms of irregular bowel habits (ASD^GI) and children with ASD who do not have a history of GI symptoms (ASD^NOGI) compared to typically developing children with GI symptoms (TD^GI) and typically developing children without a history of GI symptoms (TD^NOGI). Peripheral blood mononuclear cells (PBMC) were isolated from participant’s blood, stimulated in-vitro for 24 hrs and supernatants were assessed for cytokine production via Luminex multiplex assays. Behavioral assessments and diagnosis were performed by trained clinicians.

Results: Our data show children in the ASD^NOGI group demonstrated elevated innate immune responses, including increased levels of IL-1α, IL-1β and TNFα after stimulation with Toll-Like receptor (TLR)-4 ligands compared to TD^NOGI controls. The ASD^GI group produced increased levels of the mucosal relevant cytokines IL-5, IL-15 and IL-17 compared to ASD^NOGI following TLR-4 stimulation. The production of the regulatory cytokine TGFb1 was decreased in all stimulatory conditions in children with ASD^GI compared with children in either ASD^NOGI or TD^NOGI groups. While diagnostic scores from the ADOS were not different between ASD groups we did find that children in the ASD^GI group have worse scores on the Aberrant Behaviors Checklist (ABC) subscales in: Irritability, Hyperactivity and Social Withdrawal.  We also report finding positive correlations between TLR-4 stimulated innate cytokines IL-1 α, IL-1β and TNFα and worsening behavioral scores on the ABC.

Conclusions: While immune responses in children with ASD and GI symptoms were generally similar to children with ASD without GI symptoms, we did find evidence of reduced regulatory cytokines and increased mucosal related cytokines in the ASD^GI group that may suggest that children with ASD and GI symptoms have a unique imbalance between regulatory and inflammatory pathways.