rmjon23
2006-06-18 02:03:44 UTC
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Rat Study Shows Dirty Better Than Clean
- By SETH BORENSTEIN, AP Science Writer
Friday, June 16, 2006
(06-16) 19:56 PDT WASHINGTON, (AP) --
Gritty rats and mice living in sewers and farms seem to have healthier
immune systems than their squeaky clean cousins that frolic in cushy
antiseptic labs, two studies indicate. The lesson for humans: Clean
living may make us sick.
The studies give more weight to a 17-year-old theory that the sanitized
Western world may be partly to blame for soaring rates of human allergy
and asthma cases and some autoimmune diseases, such as Type I diabetes
and rheumatoid arthritis. The theory, called the hygiene hypothesis,
figures that people's immune systems aren't being challenged by disease
and dirt early in life, so the body's natural defenses overreact to
small irritants such as pollen.
The new studies, one of which was published Friday in the peer reviewed
Scandinavian Journal of Immunology, found significant differences in
the immune systems between euthanized wild and lab rodents.
When the immune cells in the wild rats are stimulated by researchers,
"they just don't do anything they sit there; if you give them same
stimulus to the lab rats, they go crazy," said study co-author Dr.
William Parker, a Duke University professor of experimental surgery. He
compared lab rodents to more than 50 wild rats and mice captured and
killed in cities and farms.
Also, the wild mice and rats had as much as four times higher levels of
immunoglobulins, yet weren't sick, showing an immune system tuned to
fight crucial germs, but not minor irritants, Parker said. He said what
happened in the lab rats is what likely occurs in humans: their immune
systems have got it so cushy they overreact to smallest of problems.
"Your immune system is like the person who lives in the perfect house
and has all the food they want, you're going to start worrying about
the little things like someone stepping on your flowers," Parker said.
Challenged immune systems - such as kids who grow up with two or more
pets - don't tend to develop as many allergies, said Dr. Stanley
Goldstein, director of Allergy & Asthma Care of Long Island.
Parker said his study has drawbacks because he can't be sure that the
age of the wild and lab rodents are equivalent, although he estimates
the ages based on weight. He also could not control what happened in
the past to the wild rats to see if they had unusual diseases before
being captured and killed.
It would have been more useful had Parker studied extremely young wild
rodents because, according to the hygiene hypothesis, that's when the
protection from dirty living starts, said Dr. Stuart Levy, director of
the Center for Adaptation Genetics and Drug Resistance at Tufts
University.
Human epidemiological studies have long given credence to the hygiene
theory, showing that allergy and asthma rates were higher in the
cleaner industrialized areas than in places such as Africa. Parker's
studies, looking at animal differences, may eventually help scientists
find when, where and how environmental exposure help protect against
future allergies and immune disorders, said Goldstein, and Dr. Jeffrey
Platt of the Mayo Clinic in Minn., both of whom were not part of
Parker's studies.
Parker said he hopes to build a 50-foot artificial sewer for his next
step, so that he could introduce the clean lab rats to an artificial
dirty environment and see how and when the immunity was activated.
That may be the biggest thing to come out of the wild and lab rodent
studies, Platt said: "Then all of a sudden it becomes possible to
expose people to the few things (that exercise the immune system) and
gives them the benefit of the dirty environment without having to
expose them to the dirt."
URL:
http://sfgate.com/cgi-bin/article.cgi?file=/n/a/2006/06/16/national/a113757D61.DTL
Rat Study Shows Dirty Better Than Clean
- By SETH BORENSTEIN, AP Science Writer
Friday, June 16, 2006
(06-16) 19:56 PDT WASHINGTON, (AP) --
Gritty rats and mice living in sewers and farms seem to have healthier
immune systems than their squeaky clean cousins that frolic in cushy
antiseptic labs, two studies indicate. The lesson for humans: Clean
living may make us sick.
The studies give more weight to a 17-year-old theory that the sanitized
Western world may be partly to blame for soaring rates of human allergy
and asthma cases and some autoimmune diseases, such as Type I diabetes
and rheumatoid arthritis. The theory, called the hygiene hypothesis,
figures that people's immune systems aren't being challenged by disease
and dirt early in life, so the body's natural defenses overreact to
small irritants such as pollen.
The new studies, one of which was published Friday in the peer reviewed
Scandinavian Journal of Immunology, found significant differences in
the immune systems between euthanized wild and lab rodents.
When the immune cells in the wild rats are stimulated by researchers,
"they just don't do anything they sit there; if you give them same
stimulus to the lab rats, they go crazy," said study co-author Dr.
William Parker, a Duke University professor of experimental surgery. He
compared lab rodents to more than 50 wild rats and mice captured and
killed in cities and farms.
Also, the wild mice and rats had as much as four times higher levels of
immunoglobulins, yet weren't sick, showing an immune system tuned to
fight crucial germs, but not minor irritants, Parker said. He said what
happened in the lab rats is what likely occurs in humans: their immune
systems have got it so cushy they overreact to smallest of problems.
"Your immune system is like the person who lives in the perfect house
and has all the food they want, you're going to start worrying about
the little things like someone stepping on your flowers," Parker said.
Challenged immune systems - such as kids who grow up with two or more
pets - don't tend to develop as many allergies, said Dr. Stanley
Goldstein, director of Allergy & Asthma Care of Long Island.
Parker said his study has drawbacks because he can't be sure that the
age of the wild and lab rodents are equivalent, although he estimates
the ages based on weight. He also could not control what happened in
the past to the wild rats to see if they had unusual diseases before
being captured and killed.
It would have been more useful had Parker studied extremely young wild
rodents because, according to the hygiene hypothesis, that's when the
protection from dirty living starts, said Dr. Stuart Levy, director of
the Center for Adaptation Genetics and Drug Resistance at Tufts
University.
Human epidemiological studies have long given credence to the hygiene
theory, showing that allergy and asthma rates were higher in the
cleaner industrialized areas than in places such as Africa. Parker's
studies, looking at animal differences, may eventually help scientists
find when, where and how environmental exposure help protect against
future allergies and immune disorders, said Goldstein, and Dr. Jeffrey
Platt of the Mayo Clinic in Minn., both of whom were not part of
Parker's studies.
Parker said he hopes to build a 50-foot artificial sewer for his next
step, so that he could introduce the clean lab rats to an artificial
dirty environment and see how and when the immunity was activated.
That may be the biggest thing to come out of the wild and lab rodent
studies, Platt said: "Then all of a sudden it becomes possible to
expose people to the few things (that exercise the immune system) and
gives them the benefit of the dirty environment without having to
expose them to the dirt."
URL:
http://sfgate.com/cgi-bin/article.cgi?file=/n/a/2006/06/16/national/a113757D61.DTL