OCD linked to immune system

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U. study links OCD to immune system problem

Published: Friday, May 28, 2010 12:15 a.m. MDT

SALT LAKE CITY — Research at the University of Utah may offer hope to people

with obsessive compulsive disorder, according to a report published this week.

The study, led by Nobel Prize-winning geneticist Capecchi, shows the first

cause-and-effect link between immune system cells and mental illness, which

points toward eventual new psychiatric treatments.

The research indicated that bone marrow transplants cure mutant mice that pull

out their hair compulsively. Mice share more than 99 percent of the same genes

with humans, Capecchi said, giving a strong indication that the findings would

correlate to people with similar disorders.

" We're showing there is a direct relationship between a psychiatric disorder and

the immune system, " Capecchi said.

The research focused on specific cells called microglia that are derived from

bone marrow and are found in the brain, he said.

Capecchi said the findings — published in the May 28 issue of the journal Cell —

should inspire researchers " to think about potential new immune-based therapies

for psychiatric disorders. "

Capecchi and colleagues showed that pathological grooming and hair-pulling in

mice — a disorder similar to trichotillomania in humans — is caused by a mutant

gene that results in defective microglia, which are immune system cells that

originate in bone marrow and migrate from blood to the brain. Microglia defend

the brain and spinal cord, attacking and engulfing infectious agents.

In the key experiment, researchers transplanted bone marrow from normal mice

into mice that had a mutant gene and that compulsively pulled out their own

chest, stomach and side fur. As the transplant took hold during the ensuing

months, grooming behavior became normal. Some mice recovered completely, and the

others showed extensive hair growth and healing of wounds.

" A lot of people are going to find it amazing, " says Capecchi. " That's the

surprise: Bone marrow can correct a behavioral defect. "

He cautioned that the findings do not suggest performing bone marrow transplants

for psychiatric disorders in humans.

Bone marrow transplants are expensive, and the risks and complications are so

severe they generally are used only to treat life-threatening illnesses,

including leukemia, lymphoma and disabling autoimmune diseases such as lupus, he

said.

Capecchi said that mice with the mutant gene that causes pathological grooming

now can be used to study the connections between the immune system's microglia

cells and mental illness — and ultimately to produce new treatments. However, it

will take years to conduct reliable clinical trials, he added.

" We think it's a very good model for obsessive-compulsive disorder, " he said.

Capecchi said previous studies have linked the immune system and psychiatric

disorders but not in a cause-and-effect manner.

" If you look at people who are depressed, often you find their immune system

isn't working normally, " he said.

The new findings " provide direct evidence for an association between

neuropsychiatric diseases and dysfunction of the immune system or of the

blood-forming system, " Capecchi said.

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