AUTISM is associated with inflammation of the brain, according to a small study. The finding is creating a stir among experts, who say it might even lead to ways to treat the condition.
鈥淭his is a very important contribution to our understanding of the disease,鈥� says neurologist Robert Fujinami at the University of Utah in Salt Lake City. 鈥淚t will be cited for many years to come.鈥�
At present, there is little agreement about the cause, or causes, of autism. Certain genetic variations seem to play a role, but environmental factors could also be involved. Even the question of whether the disorder is really becoming more common is controversial.
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The latest findings come from Carlos Pardo鈥檚 team at Johns Hopkins University School of Medicine in Baltimore, Maryland. They obtained samples of brain tissue from 11 people with autism aged between 5 and 44 who had been killed in accidents such as drowning, and compared them with samples from six other people. The team measured levels of 79 immune system chemicals.
In the brains of people with autism the team found consistently higher levels of certain immune messenger proteins released by support cells called astroglia and microglia (Annals of Neurology, DOI: 10.1002/ana.20315). These proteins trigger a general inflammatory response when brain cells are damaged.
Signs of inflammation were most marked in the cerebellum, a region of the brain linked with behaviour and cognition as well as movement. Brain-scanning studies have linked abnormalities here with autism.
The team also found raised levels of immune signalling proteins in the cerebrospinal fluid of people with autism, suggesting that samples of fluid taken from the spine could be used for diagnosing and monitoring the course of the condition.
The idea that autism might be caused by an immune system malfunction is just one of many proposed theories, but most past studies have focused on aspects of adaptive immunity, such as the production of antibodies to fight off invading viruses. Claims that autism may be triggered by the MMR vaccine fall into this category.
Yet Pardo鈥檚 team did not find any evidence for increased or abnormal activity in adaptive immunity. The only differences were in the inflammatory response. A growing number of studies have failed to reveal any evidence to support the claims that the MMR vaccine triggers autism (New 杏吧原创, 16 November 2002, p 7).
Pardo stresses that his team has found only a correlation between inflammation and autism. The inflammation might be causing the behavioural symptoms, or it could be helping to protect the brain.
If inflammation does turn out to be the cause, it might offer a way to treat or prevent autism. 鈥淚t suggests a chronic process that could be treated,鈥� says Catherine Lord, director of the University of Michigan Autism and Communication Disorders Center in Ann Arbor. 鈥淭his is many steps away from having immediate value for individuals with autism,鈥� she cautions. 鈥淏ut it proposes a new way of thinking about autism, that could be very, very important.鈥�
