Average levels of immune markers at birth can protect against autism

Researchers from the Karolinska Institutet studied the association between certain immune markers in newborns and the risk of later developing autism spectrum disorder (ASD). They found that average levels of a classic marker of inflammation, C-reactive protein, were associated with lower risk of ASD, while too much or not enough was linked with increased risk. The study is published in the scientific journal Biological Psychiatry.

Autism spectrum disorder onset in childhood and is a neuropsychiatric condition characterized by limited communication and social skills and repetitive behavior. Causes of ASD include genetic and environmental factors, but are still largely unknown. Previous studies have shown that severe maternal infection during pregnancy is linked to an increased risk of autism in offspring.

The current study is based on the idea that the developing brain may be particularly vulnerable to immune signaling disorders in connection with exposure to environmental factors. The researchers studied a number of molecules called acute phase proteins that are an important part of the innate immune system, our first line of defense against infections, especially during early childhood. These proteins circulate in our bloodstream and can rapidly increase after exposure to infection. One example is C-reactive protein (CRP), commonly used as a marker of inflammation in healthcare.

It can be a bad thing for the developing brain

For the observational study, blood samples from nearly 1,000 children with ASD, over 200 of their unaffected siblings, and over 1,000 healthy controls from a Swedish health registry were analyzed. Children with high CRP levels were at a higher risk of later developing ASD. Surprisingly, low CRP levels were also associated with an increased risk, while mean CRP levels were associated with the lowest risk.

“This means that too much inflammation may actually be a bad thing for the developing brain, but it may be too little,” says lead author Renee Gardner, a researcher at the Department of Global Public Health, Karolinska Institutet. “Among infants whose mothers had been hospitalized for an infection during pregnancy, those who were able to produce a little more of these acute phase proteins tended to have a lower risk of autism. So it appears. that a greater ability to respond to the surrounding environment could result in a lower risk of autism. “

Lower levels than their brothers

The children with ASD had lower levels of the immune markers at birth than their unaffected siblings.

“This is interesting because siblings share about half of their DNA and the environment within the womb and during the first few days of life it is likely similar between siblings,” says Renee Gardner.

The study cannot answer the question of whether immune activation is a contributor or a marker of autism risk.