A new study by scientists at Johns Hopkins shows that brain inflammation is a sign of autism. The findings are reported in the online edition of Annals of Neurology, the scientific journal of the American Neurological Association.
Strong evidence that certain immune system components that promote inflammation are consistently activated in people with autism was unearthed.
"These findings reinforce the theory that immune activation in the brain is involved in autism, although it is not yet clear whether it is destructive or beneficial, or both, to the developing brain," said senior author Carlos A. Pardo-Villamizar, M.D., at the Johns Hopkins University School of Medicine in Baltimore, Maryland.
Autism is a brain disorder that begins in early childhood and persists throughout adulthood; affects three crucial areas of development: communication, social interaction, and creative or imaginative play. It is estimated to afflict between 2 and 5 of every 1000 children and is four times more likely to strike boys than girls. Children with autism have difficulties in social interaction and communication and may show repetitive behaviors and have unusual attachments to objects or routines.
Autism has a strong genetic component, and in some families, autism tends to be more prevalent. In identical twins with autism both are usually affected. However, the number of children with autism appears to be increasing more than expected for a genetic disorder. This suggests to scientists that genetic abnormalities require the influence of other factors to cause the disorder. Birth complications, toxins, diet, and viruses and other pathogens have been suggested, though there is no strong evidence for any of these.
In recent years, there have been scientific hints of immune system irregularities in children with autism, but not all studies have confirmed this. Pardo and his colleagues sought a more definitive answer by looking not at the immune system overall, but at immune components inside the relatively sealed environment of the nervous system.
Led by first author Diana L. Vargas, MD, a post-doctoral fellow working in Pardo's laboratory, the researchers examined brain tissue from 11 people with autism, aged 5 to 44 years, who had died of accidents or injuries.
Compared with normal control brains, the brains of the people with autism featured immune system activation and inflammation in the brain.
"This ongoing inflammatory process was present in different areas of the brain and produced by cells known as microglia and astroglia," said Pardo.
When the researchers measured brain levels of immune system proteins called cytokines and chemokines, they found abnormal patterns consistent with inflammation.