A Johns Hopkins study has found new evidence that the
brains of some people with autism show clear signs of
inflammation, suggesting that the disease may be associated
with activation of the brain's immune system.
"These findings reinforce the theory that immune
response in the brain is involved in autism, although it is
not yet clear whether the inflammation is a consequence of
disease, or a cause of it or both," said Carlos
Pardo-Villamizar, assistant professor of
neurology and
pathology in the
School of Medicine and senior author of a report on the
study published early online Nov. 15 in the journal
Annals of Neurology.
Whatever the cause of the inflammation, it may provide
a good target for developing new treatments, Pardo said.
Autism is a disorder of the developing brain that
appears in early childhood. According to the American
Neurological Association, it is estimated to afflict
between two and five of every 1,000 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 in some
families, although other causes likely play a role,
possibly including birth complications, diet, toxins or
infections, Pardo said.
"Scientists have found hints that the immune system
may be involved in autism, but not all studies have
confirmed this," he said. "We wanted a more definitive
answer, so rather than looking at the overall immune
system, we focused on immune responses inside the
relatively sealed environment of the nervous system."
Led by first author Diana L. Vargas, a postdoctoral
fellow working in Pardo's laboratory, the researchers
examined tissue from three different regions of the brain
in 11 people with autism, ages 5 to 44, who had died of
accidents or injuries. They also measured levels of two
immune system proteins, cytokines and chemokines, found in
the cerebrospinal fluid — the clear substance that
surrounds, bathes and nourishes the brain and spinal cord
— in six living patients with autism, ages 5 to
12.
Compared with normal control brains, the brains of
people with autism showed evidence of an ongoing
inflammatory process in different regions of the brain and
produced by cells known as microglia and astroglia, Pardo
said. Cytokine and chemokine levels in the cerebrospinal
fluid also were abnormally elevated in patients with
autism.
"These findings suggest that the inflammation is
localized to specific regions within the brain and not
caused by immune system abnormalities from outside the
brain," Pardo said.
Pardo and colleagues are now studying how the genetic
background of patients and families may influence immune
system reactions in the brain associated with autism.
Other authors are Andrew Zimmerman, Caterina
Nascimbene and Chitra Krishnan. The study was funded by the
Cure Autism Now Foundation, the Autism Research Foundation,
the National Institutes of Health, Dr. Barry and Renee
Gordon and an anonymous donor.
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