Immune Cells Help Maintain Cognition, etc.

[Guest guest]

A

Immune Cells Help Maintain Cognition, etc.

Fri, 20 Jan 2006 15:41:13 +0000

 

 

 

 

Scientists Suggest That Immune Cells Help to Maintain Cognition and

Brain Cell Renewal ImmuneSupport.com

 

01-18-2006

 

Source: American Committee for the Weizmann Institute of Science

 

A team of scientists at the Weizmann Institute of Science, led by

Prof. Michal Schwartz of the Neurobiology Department, has come up with

new findings that may have implications in delaying and slowing down

cognitive deterioration in old age. The basis for these developments

is Schwartz's team's observations, published today in the February

issue of Nature Neuroscience, that immune cells contribute to

maintaining the brain's ability to maintain cognitive ability and cell

renewal throughout life.

 

Until quite recently, it was generally believed that each individual

is born with a fixed number of nerve cells in the brain, and that

these cells gradually degenerate and die during the person's lifetime

and cannot be replaced.

 

This theory was disproved when researchers discovered that certain

regions of the adult brain do in fact retain their ability to support

and promote cell renewal (neurogenesis) throughout life, especially

under conditions of mental stimuli and physical activity. One such

brain region is the hippocampus, which subserves certain memory

functions. But how the body delivers the message instructing the brain

to step up its formation of new cells is yet unknown.

 

The central nervous system (CNS), comprising the brain and spinal

cord, has been considered for a long time as " a forbidden city " , in

which the immune system is denied entry as its activity is perceived

as a possible threat to the complex and dynamic nerve cell networks.

Furthermore, immune cells that recognize the brain's own

components( " autoimmune " cells) are viewed as a real danger as they can

induce autoimmune diseases.

 

Thus, although autoimmune cells are often detected in the healthy

individual, their presence there was perceived as an outcome of the

body's failure to eliminate them. But Schwartz's group showed that

these autoimmune cells have the potential ability – if their levels

are controlled – to fight off debilitating degenerative conditions

that can afflict the CNS, such as Alzheimer's and Parkinson's

diseases, glaucoma, amyotrophic lateral sclerosis (ALS), and the nerve

degeneration that results from trauma or stroke.

 

In their earlier research, Schwartz and her team provided evidence to

suggest that T cells directed against CNS components do not attack the

brain but instead, recruit the help of the brain's own resident immune

cells to safely fight off any outflow of toxic substances from damaged

nerve tissues.

 

In the present study, the scientists showed that the same immune cells

may also be key players in the body's maintenance of the normal

healthy brain. Their findings led them to suspect that the primary

role of the immune system's T cells (which recognize brain proteins)

is to enable the " neurogenic " brain regions (such as the hippocampus)

to form new nerve cells, and maintaining the individual's cognitive

capacity.

 

The research team led by Prof. Schwartz, included graduate students

Yaniv Ziv, Noga Ron and Oleg Butovsky, and in collaboration with

former graduate student Dr. Jonathan Kipnis and with Dr. Hagit Cohen

of the Ben-Gurion University of the Negev, Beer Sheva.

 

It was reported before that rats kept in an environment rich with

mental stimulations and opportunities for physical activity exhibit

increased formation of new nerve cells in the hippocampus. In the

present work, the scientists showed for the first time that formation

of these new nerve cells following environmental enrichment is linked

to local immune activity. To find out whether T cells play a role in

this process they repeated the experiment using mice with severe

combined immune deficiency (scid mice), which lack T cells and other

important immune cells.

 

Significantly fewer new cells were formed in those mice. On repeating

the same experiment, this time with mice possessing all of the

important immune cells except for T cells, they again found impairment

of brain-cell renewal, confirming that the missing T cells were an

essential requirement for neurogenesis. They observed that the

specific T cells that are helping the formation of new neurons are the

ones recognizing CNS proteins.

 

To substantiate their observations, the scientists injected T cells

into immune-deficient mice with the objective of replenishing their

immune systems. The results: cell renewal in the injected mice was

partially restored – a finding that supported their theory.

 

In another set of experiments, they found that mice possessing the

relevant CNS-specific T cells performed better in some memory tasks

than mice lacking CNS-specific T cells. Based on these findings, the

scientists suggest that the presence of CNS-specific T cells in mice

plays a role in maintaining learning and memory abilities in adulthood.

 

Schwartz points out that the role of the autoimmune T cells is not to

affect the level of intelligence or motivation, but rather, to allow

the organism to achieve the full potential of its brainpower. " These

findings, " she says, " give a new meaning to 'a healthy mind in a

healthy body'. They show that we rely on our immune system to maintain

brain functionality, and so they open up exciting new prospects for

the treatment of cognitive loss. "

 

Knowledge that the immune system contributes to nerve cell renewal has

potential far-reaching implications for elderly populations, because

aging is known to be associated with a decrease in immune system

function. It is also accompanied by a decrease in new brain cell

formation, as well as in memory skills.

 

Therefore, by manipulating and boosting the immune system, it might be

possible to prevent or at least slow down age-related loss of memory

and learning abilities.

 

Prof. Michal Schwartz's research is supported by the Nella and Leon

Benoziyo Center for Neurological Diseases; the Alan T. Brown

Foundation to Cure Paralysis; the Carl and Micaela Einhorn-Dominic

Institute for Brain Research; Mr. and Mrs. Irwin Green, Boca Raton,

FL; and Mr. and Mrs. Richard D. Siegal, New York, NY.

 

Prof. Schwartz is the incumbent of the Maurice and Ilse Katz

Professorial Chair of Neuroimmunolgy.

 

The Weizmann Institute of Science in Rehovot, Israel, is one of the

world's top-ranking multidisciplinary research institutions. Noted for

its wide-ranging exploration of the natural and exact sciences, the

Institute is home to 2,500 scientists, students, technicians and

supporting staff. Institute research efforts include the search for

new ways of fighting disease and hunger, examining leading questions

in mathematics and computer science, probing the physics of matter and

the universe, creating novel materials and developing new strategies

for protecting the environment.