Reduced levels of immunoglobulin in children with autism correlateswith behavioral symptoms

Objectives: To assay if plasma antibody levels in children with autism or developmental delays (DD) differ from those withtypical development as an indicator of immune function and to correlate antibody levels with severity of behavioralsymptoms. Methods: Plasma was collected from children with autistic disorder (AU; n=116), DD but not autism (n=32), autismspectrum disorder but not full autism (n=27), and age-matched typically developing (TD) controls (n=96). Sampleswere assayed for systemic levels of immunoglobulin (IgG, IgM, IgA, and IgE) by enzyme-linked immunosorbent assay. Subjects with autism were evaluated using the Autism Diagnostic Observation Schedule and the Autism DiagnosticInterview-Revised, and all subjects were scored on the Aberrant Behavior Checklist (ABC) by the parents. Numericalscores for each of the ABC subscales as well as the total scores were then correlated with Ig levels.Results: Children with AU have a significantly reduced level of plasma IgG (5.39±0.29 mg/mL) compared to the TD(7.72±0.28 mg/mL; P<0.001) and DD children (8.23±0.49 mg/mL; P<0.001). Children with autism also had a reducedlevel of plasma IgM (0.670.06mg/mL) compared to TD (0.79±0.05 mg/mL; P<0.05). Ig levels were negatively correlatedwith ABC scores for all children (IgG: r=±0.334, P<0.0001; IgM: r=-0.167, P=0.0285). Conclusion: Children with AU have significantly reduced levels of plasma IgG and IgM compared to both DD and TDcontrols, suggesting an underlying defect in immune function. This reduction in specific Ig levels correlates withbehavioral severity, where those patients with the highest scores in the behavioral battery have the most reduced levels ofIgG and IgM.