Study explores autism link to immune system

In another tantalizing link between the immune system and autism, UC Davis researchers have found 11 genes, all governing "natural killer" immune cells, that are more active in autistic children than in other youngsters.

While the study is small and very preliminary, it bolsters theories that some sort of infectious agent, early in life or even in the womb, might play a role in autism, said Dr. Jeffrey Gregg, director of molecular diagnostics for the UC Davis Medical Center.

Gregg is one of 11 researchers who studied how genes are expressed in the blood of children with and without autism.

Their work, being published in the January edition of Genomics, found similarities in all autistic youngsters, as well as intriguing differences between those whose symptoms show up earlier or later.

Both findings could eventually lead to a better understanding of how different types of autism develop, as well as potential tools for diagnosing or preventing the neurodevelopmental disorder, Gregg said.

People with autism have trouble connecting with others in a wide range of ways, such as failing to make eye contact or understand facial expressions or gestures. They may engage in repetitive or destructive behaviors.

Sometimes the symptoms become obvious very early, when babies fail to hit normal developmental markers, but in other cases children develop typically for 18 months or more, then seem to slip backward.

Children with that "regressive" autism had nearly 500 genes that were activated differently than children with "early onset" autism, Gregg and his colleagues found after examining blood samples from 61 children.

"That would suggest that those two groups are very different … and may have totally different underlying pathology," Gregg said.

Both groups, though, as well as other children with a range of symptoms called autism spectrum disorder, shared the 11 strongly expressed genes that control natural killer immune cells.

Some of the genes were also involved in other immune functions.

Because researchers set out to make such a broad study of the blood, looking at how every gene was expressed, Gregg said it was "fairly startling and provocative" to see the relationship with natural killer cells emerge.

The new research follows earlier suggestions of an autism- immune system link, including a 2005 analysis by other researchers at the UC Davis MIND Institute looking at proteins in the blood.

That work found autistic children had 20 percent more B cells, an immune cell that produces antibodies, and 40 percent more natural killer cells, which attack tumors, viruses and other invaders.

It is still unclear how early those differences emerge, but other MIND Institute researchers are looking at immune differences in mothers' bloodstreams that might be predictive for having a child with autism, said Dr. David Amaral, the institute's research director.

"Things are moving really, really fast now," Amaral said, with scientists around the country working to understand the relationship of genetic and environmental factors that may underlie autism.

"It gives me optimism that we're going to find a variety of useful markers for prevention and maybe even treatment as well," he said.

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