A new study shows that it may be the mother's production of antibodies against her baby's brain tissue during pregnancy that triggers autism in the fetus.
Autism is a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behavior, all starting before a child is three years old.
"Now our research suggests that the mother's immune system may be yet another factor or a trigger in those already predisposed," said Harvey Singer, M.D., director of pediatric neurology at Hopkins Children's Center investigators and the study's lead researcher.
Antibodies are proteins the body makes in response to viruses and bacteria or sometimes mistakenly against its own tissues. Yet, the majority of children with autism have no clinical evidence of autoimmune diseases, which prompted researchers to wonder whether the antibodies transferred from mother to child during pregnancy could interfere with the fetal brain directly.
To test their theory, the research team used a technique called immunoblotting in which antibodies derived from blood samples are exposed to adult and fetal brain tissue to check whether the antibodies recognize and react against specific brain proteins.
Comparing the antibody-brain interaction in samples obtained from 100 mothers of autistic children and 100 mothers of children without autism, researchers found either stronger reactivity or more areas of reactivity between antibodies and brain proteins in about 40 percent of the samples obtained from the mothers of autistic children.
Further, the presence of maternal antibodies was associated with so-called developmental regression in children, increasingly immature behaviors that are a hallmark of autism.
"The mere fact that a pregnant woman has antibodies against the fetal brain doesn't mean she will have an autistic child. Autism is a complex condition and one that is likely caused by the interplay of immune, genetic and environmental factors," Singer said.
Researchers caution that the findings needn't be cause for alarm, but should be viewed instead as a step forward in untangling the complex nature of autism.
The study is published in the Journal of Neuroimmunology.