In the brains of people with autism, microglial cells appear to be constantly activated, with genes for inflammation responses perpetually turned on, according to a new collaborative study by researchers at Johns Hopkins University School of Medicine and the University of Alabama at Birmingham.
There are too many factors and combinations of genetic traits to have any definitive cause of autism today, along with a wide range of diagnoses that add to the pool, but a new analysis has found that the autopsied brains of people who had autism share a pattern of ramped-up immune responses.
The causes of autism, also known as autistic spectrum disorder, remain largely unknown and are a frequent research topic for geneticists and neuroscientists. The authors of a new paper note that for autism, studiesof whether and how much genes were being used - known as gene expression - had thus far involved too little data to draw many useful conclusions. That's because unlike a genetic test, which can be done using nearly any cells in the body, gene expression testing has to be performed on the specific tissue of interest; in this case, brains that could only be obtained through autopsies.
"There are many different ways of getting autism, but we found that they all have the same downstream effect," Dan Arking, Ph.D., an associate professor in the McKusick-Nathans Institute for Genetic Medicine at the Johns Hopkins University School of Medicine said in a statement. "What we don't know is whether this immune response is making things better in the short term and worse in the long term."
Inflammation is not likely a root cause of autism, but a consequence of a gene mutation, Arking stressed. To better understand inflammation's effects, researchers will want to find out whether treating it makes autism symptoms any better, he said.
Autism is the most severe of a range of neurological and developmental disorders classified as autism spectrum disorder (ASD). The most common symptom of autismis difficulty with social interactions, such as discomfort with eye contact and trouble interpreting social cues. Although researchers have identified certain genes and areas of the brain associated with the disorder, it's likely that environment also plays a role in causing autism.
"This type of inflammation is not well understood, but it highlights the lack of current understanding about how innate immunity controls neural circuits," said Andrew West, Ph.D., an associate professor of neurology at the University of Alabama.
