http://www.sciencenews.org/view/generic/id/31443/title/Triggering_autoimmune=
_assaults
Triggering autoimmune assaults
By Janet Raloff
April 24th, 2008
Mouth bacteria unleash inflammation-inducing protein
SAN DIEGO =97 Our bodies provide food and shelter for trillions of
microbes =97 bacteria, yeasts and other squatters. Now, researchers
re****t that a few resident species release a substance that can
inappropriately rev up the immune system. If this happens at the wrong
time, animal tests suggest, the body may launch a dangerous assault
against itself.
Once such an autoimmune attack begins, the body finds it hard to shut
it down, notes Robert B. Clark. The question has always been what
triggers autoimmunity =97 the condition underlying multiple sclerosis,
rheumatoid arthritis, inflammatory bowel disease and a host of other
disorders.
Clark=92s team, at the University of Connecticut Health Center in
Farmington, has stumbled onto one new candidate culprit. It=92s a fatty
compound =97 phosphoethanolamine dihydroceramide, or PEDHC for short =97
produced by bacteria residing in the human mouth. The researchers
learned about it from a dental colleague, Frank Nichols, who noticed
that it caused inflammation in test tube studies and showed up in
human tissues that experienced inflammation.
Curious about whether it might affect autoimmunity, Clark=92s group
tested PEDHC in a mouse model for MS known as experimental autoimmune
encephalomyelitis.
To bring on the disease, researchers inject rodents with an emulsion
containing brain proteins together with a chemical that enhances
immunity. Soon, immune machinery in the mice begins mistaking the
brain proteins as alien and attacks them. Immune scouts find plenty
more of the =93alien=94 proteins in the rodents=92 actual brains,
unlea****ng=
autoimmune disease there within 12 to 17 days.
The induced autoimmunity develops two to four days earlier and is far
more severe in animals that also receive PEDHC, even in trace amounts,
the immunologists re****ted in April in San Diego at the Experimental
Biology meeting.
=2E..
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Luke
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