Immune 'invisibility' of brain stem cells proven

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Immune 'invisibility' of brain stem cells proven

17:10 18 July 03

NewScientist.com news service

http://www.newscientist.com/news/news.jsp?id=ns99993953

Stem cells from the brain do not provoke an immune response when

transplanted to different parts of another individual's body, suggests

a study in mice.

The finding could help overcome immune rejection, one of the most

difficult obstacles to developing therapies to treat people with

central nervous system problems such as spinal cord injuries and

Parkinson's disease.

Young, at the Schepens Eye Research Institute, Harvard, and US

and Japanese colleagues have shown that stem cells from the brain have

a special " immune privilege " even when they are transplanted to places

outside their normal location in the central nervous system.

The team found that stem cells transplanted from the brains of mice to

the kidney capsules of mice of a different strain not only survived,

but developed into mature tissue.

" These findings are very exciting, " says Young. " Though we suspected

brain stem cells might be protected in this way, this is the first

documented evidence. "

The study is " encouraging " says Kerr, a neurobiologist at

s Hopkins University in Baltimore, land, who is researching

applications of embryonic stem cells in spinal cord injury. If the

results are reproducible " it would certainly make a human application

more likely " , he told New Scientist.

Stern test

Special sites within the body are known to have " immune privilege " .

The body's immune system does not mount an attack against foreign

invaders in these areas - which includes the eye, brain and

reproductive system - as these tissues are so delicate that

inflammation caused by a response would destroy their function.

As a stern test of the immune properties of stem cells from the brain,

the team transplanted the cells to a part of the body - the kidney

capsule - known to always reject foreign tissue unless the tissue is

closely matched or immunosuppressant drugs are given.

Stem cells were taken from the brains of so-called " green mice " which

have a jellyfish gene for a green protein inserted in their DNA. These

were then transplanted to the kidney capsules of normal mice.

The green cells were not rejected in any of the mice after four weeks,

and in fact had grown into neural tissue. But Young told New Scientist

that the team were not surprised at this: " We really anticipated that

these were going to be really cool cells from an immunological

perspective. "

Identity tag

What did surprise the team was that further tests revealed that even

though the stem cells had antigens on their surface - molecules which

should have identified them as foreign - they appeared to be invisible

to the immune system.

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Weblinks

Young, Schepens Eye Research Institute

Cloning and stem cells, New Scientist

Stem Cells

" These really have important implications for the ultimate success of

stem cell transplantation, " Young says.

Kerr agrees that tackling immunosuppression is key. He says that

people with CNS disorders like stroke or spinal injury are already

more susceptible to infection. " This is a high risk population to

immunosuppress, so it's really been a barrier in terms of human

trials, " he told New Scientist.

Another type of immune privileged stem cell is being investigated by

Osiris Therapeutics in Baltimore and others (New Scientist print

edition, 15 December 2001). These are called " mesenchymal stem cells "

(MSCs) and are taken from bone marrow. These cells have been shown to

develop into six kinds of tissue, including bone, cartilage, tendon

and muscle but not the neural cells that Young's team studied.

Journal reference: Stem Cells (vol 21, p 405)

Shaoni Bhattacharya