Autism and Immunity: Salivary Cytokines in Children with Autism Spectrum Disorder

Background: Many individuals with ASD demonstrate skewed immune profiles, suggestive of a potential role for immune dysfunction (Noriega & Savelkoul, 2014). Elevated immune mediators such as cytokines have been found in the blood plasma, cerebral spinal fluid, gastrointestinal track, and post-mortem brain tissue of individuals with ASD (Ashwood et al., 2011; DeFelice et al., 2003; Molloy et al., 2006). Genetic studies have uncovered a host of potential immune regulatory related genes altered in ASD, while research on maternal immune activation during fetal development has also been implicated in immune dysregulation in ASD (Patterson, 2011). Other research suggests that volumetric differences, morphological differences, and abnormal neuroinflammation in ASD may be related to neuroimmune factors such as elevated cytokines (Wei, Alberts, & Li, 2013). The study of those with skewed immune panels is crucial for discerning the interaction between the immune system during neurodevelopment and its potential involvement in ASD.

Objectives: This study aims to assess if the inflammatory cytokines interleukin-6 (IL-6) and interleukin 1 beta (IL-1β) are elevated in the saliva of low functioning children with ASD as compared to typically developing control children. This study also aims to explore the relationship between elevated salivary cytokines in autism and the severity of autistic symptoms.

Methods: Twenty-five low-functioning children with ASD and twenty-eight typically developing control children from 6-18 years of age were enrolled in the current study. Salivary samples were collected using the SalivaBio Children’s Swab (SCS) Method, which consists of placing a soft swab inside the mouth for 60 – 90 seconds. Salivary IL-6 and Salivary IL-1β levels were flow-rate controlled and measured via enzyme-linked imunnosorbent assays (ELISA) with a 450 nm plate reader. The Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) was administered to children with autism in order to determine severity of ASD. 

Results: Salivary IL-6 was significantly elevated in children with ASD (μ= 7.3082 pg/mL) as compared to typically developing control children (μ= 2.691 pg/mL), (t= 2.3444; P=0.0283). There was no significant difference between children with autism (μ=235.28 pg/mL) and typically developing children’s salivary IL-1β levels (μ=212.12 pg/mL), (t=.342; p=.735). There was a weak positive correlation between salivary IL-6 levels and ADOS-2 raw scores in ASD children with detectable levels of salivary IL-6 (R= 0.1495). There was also a weak positive correlation between salivary IL-1β levels and ADOS-2 raw scores in ASD children (R=0.1939).

Conclusions: Consistent with related studies, our findings are suggestive of a potential role for immune dysfunction in ASD. To our knowledge there are no published studies that have investigated salivary IL-6 or IL-1 β in individuals with ASD. Previous studies have found relationships between salivary IL-6 and psychosocial factors, immune functioning, stress, and sleep dysfunction (El-Sheikh et al., 2007; Groer et al., 2010; Ris et al., 2015 Sjögren et al., 2006) as well as relationships between salivary IL-1 β and inflammatory conditions (Hernández-Rodríguez et al., 2004; Southerland et al., 2006). Future studies should attempt to correlate blood plasma levels of cytokines to salivary levels of cytokines within same ASD population.