Background. Research on the biological pathophysiology of autism has found some evidence that immune alterations may play a role in the pathophysiology of that illness. As a consequence we expected to find that autism is accompanied by abnormalities in the pattern obtained in serum protein electrophoresis and in the serum immunoglobulin (Ig) and IgG subclass profile.

Method. We examined whether subjects with autism showed changes in total serum protein (TSP) and the serum concentrations of albumin, α1 globulin, α2 globulin, β globulin and γ globulins, IgA, IgM and IgG and the IgG subclasses IgG1, IgG2, IgG3 and IgG4, compared with normal controls.

Results. We found significantly increased concentrations of TSP in autistic subjects, which were attributable to increased serum concentrations of albumin and γ globulin. Serum IgG, IgG2 and IgG4 were also significantly raised. In autism there were significant and positive correlations between social problems and TSP and serum γ globulin and between withdrawal symptoms and TSP and serum albumin and IgG.

Conclusions. The results suggest that autism is characterized by increased TSP, a unique pattern obtained in serum protein electrophoresis, i.e. increased serum albumin and IgG, and by a specific IgG subclass profile, i.e. increased serum IgG2 and IgG4. The increased serum concentrations of IgGs in autism may point towards an underlying autoimmune disorder and/or an enhanced susceptibility to infections resulting in chronic viral infections, whereas the IgG subclass skewing may reflect different cytokine-dependent influences on autoimmune B cells and their products.