Serum and salivary immunoglobulin G4 levels in children with autism spectrum disorder from south India: a case-control study.

Background: Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with wide spectrum of symptoms and few effective therapies. Evidence is suggestive of an association between immune system dysfunction and autism spectrum disorders (ASD) among children with ASD. Immunoglobulins (Ig) are found to be increased in the circulation of individuals with autism. The prospective study was aimed to estimate and correlate the levels of IgG4 in blood and saliva of children with autism.

Methodology: Blood and unstimulated saliva were collected from 172 children (55 ASD, 57 healthy control, and 60 suspected parasitic infection) aged 0-18 years. Routine blood investigations were done. Serum and salivary IgG4 levels were analyzed using a commercially available enzyme-linked immunosorbent assay (ELISA) kit. Data were subjected to statistical analysis.

Results: ELISA tests showed that the IgG4 levels in serum and saliva were significantly increased (P<0.05) in children with ASD as compared to normal control children. Both serum and saliva IgG4 levels showed a significant positive correlation (P<0.05).

Conclusion: IgG4 can be used as a potential biomarker for the early detection of ASD. Further, saliva can be a diagnostic, noninvasive assessment tool for health monitoring of children with autism. Lay summary: The collection of saliva is easy and painless compared to other sample collection methods. The present study shows that, among children with autism, brain-reactive antibody, immunoglobulin G4 (gG4), is increased both in blood and saliva, and there is a significant correlation between the two levels. Therefore, the study recommends IgG4 as a potential biomarker for the early detection of autism, and saliva can be helpful in diagnosis and health monitoring of children with ASD.