Germs are a necessary part of a healthy immune system, helping our body's defenses beef up and fight future illnesses. When a person's exposure to germs is decreased, problems may arise.
We've known for a while that people who grow up on farms are less likely to have ailments related to the immune system than people who grow up in cities. Those include asthma, allergies, inflammatory bowel disease and multiple sclerosis.
Exposure to germs as a kid seems to be helpful, while living in an environment that's squeaky clean seems to pose risks for some illnesses. Still, nobody knew precisely why. But now some scientists say they think they've figured out the details of the "hygiene hypothesis."
They found that microbes in the gut keep a rare part of the immune system reined in. No microbes, and the immune cells go crazy in the lungs and intestines, increasing the risk of asthma and colitis. Add in the microbes, and cells in question, invariant natural killer T cells, retreat.
The discovery was one of those lovely "aha" moments in science. Or as says Richard Blumberg, the chief of gastroenterology at Brigham and Woman's Hospital in Boston, and co-author of the study says: "We made the serendipitous observation that these cells were dramatically enriched in the lung and colon in mice that lacked any microbes."
These are mice raised in totally germ-free environments in the lab. What really piqued the scientists' interest was that the immune response in the super-clean mouse innards looked very similar to what happens in diseases like asthma.
But they were still missing the connection with exposure to bacteria in early childhood. So Blumberg and his colleagues took pregnant germ-free mice and exposed them to microbes the day before they gave birth. The baby mice had fewer iNKT cells in their guts, even after they grew up.
The researchers also found that genetically altered mice without the iNKT cells don't get colitis, even if they were raised in a germ-free environment.
As far as the hygiene hypothesis is concerned, this abundance of bacteria is a good thing, since it helps exercise our immune system.
"But as we moved into the 1950s and '60s and '70s, and as we in the developed world became progressively hygienic, we began to think that we wish to protect ourselves, particularly fragile newborn babies, from anything that might be microbial," said Dr. William Schaffner, chairman of preventive medicine at Vanderbilt University Medical Center. "And that turns out to be obviously what we might call an overreaction."
It's unclear which microbes help regulate the immune cells, according to Dennis Kasper, director of the Channing Laboratory at Brigham and Women's, and a co-author of the study, which was published online in Science. Figuring that out is very important, he says. "You can't just put any piece of dirt into a baby and direct the control of the immune system," he says.
He thinks there are a very few special molecules in the 500 to 1,000 species in the intestine that control the immune cells, but it's going to take a lot more work to figure that out.
Of course, this study was done in mice, but it gets at some fundamental questions that would be impossible ask in humans. No germ-free cages for us.
And their findings square with 20 years of epidemiological research showing that exposure to microbes and parasites in childhood reduces the risk of autoimmune disease.
There's evidence that children who are given antibiotics early in life are more likely to have immune-based problems like asthma and food allergies. There's even some evidence that women might have more autoimmune diseases than men because they're kept cleaner than boys as children.
These disorders are more common in developed countries, and in people who move from the developing world into tidier lands.
So parents may someday emulate the germy mouse world, rather than a scrubbed and sterile environment, to ensure the health of their offspring.
Childhood exposure to bacteria and other germs may help build immunity to various microbes later on in life, researchers from Brigham and Women’s Hospital (BWH) claim in a new study.
According to Carrie Gann of ABC News, this belief is known as the “hygiene hypothesis,” and suggests — in contrast to the common belief that people should strive to remain germ free regardless of circumstances — that bacteria and other germs may be “a necessary part of a healthy immune system, helping our body’s defenses beef up and fight future illnesses. When a person’s exposure to germs is decreased, problems may arise.”
In a press release detailing their findings, the BWH experts say that the hygiene hypothesis helps to explain the increase of allergic reactions and auto-immune diseases in cities throughout the world, and that medical professionals have claimed that various sociological and environmental changes, such as the use of antibiotics among younger patients, have contributed to this phenomenon.
However, no scientific study had ever discovered a biological basis for this belief. They say that their study, which was published Thursday in Science Express, changes that.
“The researchers show that in mice, exposure to microbes in early life can reduce the body’s inventory of invariant natural killer T (iNKT) cells, which help to fight infection but can also turn on the body, causing a range of disorders such as asthma or inflammatory bowel disease,” Nature‘s Helen Thompson reported on March 22.
The BWH researchers report that, after studying the immune systems of both “germ-free mice” and those who have received normal exposure to bacteria and other microbes, they discovered that the germ-free mice “had exaggerated inflammation of the lungs and colon resembling asthma and colitis, respectively.”
“Most importantly, the researchers discovered that exposing the germ-free mice to microbes during their first weeks of life, but not when exposed later in adult life, led to a normalized immune system and prevention of diseases,” they added. “Moreover, the protection provided by early-life exposure to microbes was long-lasting, as predicted by the hygiene hypothesis.”
The researchers warn that additional research is required to see whether or not the hypothesis holds true for humans as well, but according to Gann, experts claim that the biological mechanism analyzed in the mice during this study is similar in people.
Likewise, Erika Von Mutius, head of the Munich University Children’s Hospital Asthma and Allergy Department, told Nature that the findings “complement what we see in epidemiology… It supports the idea that the microbiome is very important and the age of exposure is decisive.”
We've known for a while that people who grow up on farms are less likely to have ailments related to the immune system than people who grow up in cities. Those include asthma, allergies, inflammatory bowel disease and multiple sclerosis.
Exposure to germs as a kid seems to be helpful, while living in an environment that's squeaky clean seems to pose risks for some illnesses. Still, nobody knew precisely why. But now some scientists say they think they've figured out the details of the "hygiene hypothesis."
They found that microbes in the gut keep a rare part of the immune system reined in. No microbes, and the immune cells go crazy in the lungs and intestines, increasing the risk of asthma and colitis. Add in the microbes, and cells in question, invariant natural killer T cells, retreat.
The discovery was one of those lovely "aha" moments in science. Or as says Richard Blumberg, the chief of gastroenterology at Brigham and Woman's Hospital in Boston, and co-author of the study says: "We made the serendipitous observation that these cells were dramatically enriched in the lung and colon in mice that lacked any microbes."
These are mice raised in totally germ-free environments in the lab. What really piqued the scientists' interest was that the immune response in the super-clean mouse innards looked very similar to what happens in diseases like asthma.
But they were still missing the connection with exposure to bacteria in early childhood. So Blumberg and his colleagues took pregnant germ-free mice and exposed them to microbes the day before they gave birth. The baby mice had fewer iNKT cells in their guts, even after they grew up.
The researchers also found that genetically altered mice without the iNKT cells don't get colitis, even if they were raised in a germ-free environment.
As far as the hygiene hypothesis is concerned, this abundance of bacteria is a good thing, since it helps exercise our immune system.
"But as we moved into the 1950s and '60s and '70s, and as we in the developed world became progressively hygienic, we began to think that we wish to protect ourselves, particularly fragile newborn babies, from anything that might be microbial," said Dr. William Schaffner, chairman of preventive medicine at Vanderbilt University Medical Center. "And that turns out to be obviously what we might call an overreaction."
It's unclear which microbes help regulate the immune cells, according to Dennis Kasper, director of the Channing Laboratory at Brigham and Women's, and a co-author of the study, which was published online in Science. Figuring that out is very important, he says. "You can't just put any piece of dirt into a baby and direct the control of the immune system," he says.
He thinks there are a very few special molecules in the 500 to 1,000 species in the intestine that control the immune cells, but it's going to take a lot more work to figure that out.
Of course, this study was done in mice, but it gets at some fundamental questions that would be impossible ask in humans. No germ-free cages for us.
And their findings square with 20 years of epidemiological research showing that exposure to microbes and parasites in childhood reduces the risk of autoimmune disease.
There's evidence that children who are given antibiotics early in life are more likely to have immune-based problems like asthma and food allergies. There's even some evidence that women might have more autoimmune diseases than men because they're kept cleaner than boys as children.
These disorders are more common in developed countries, and in people who move from the developing world into tidier lands.
So parents may someday emulate the germy mouse world, rather than a scrubbed and sterile environment, to ensure the health of their offspring.
Childhood exposure to bacteria and other germs may help build immunity to various microbes later on in life, researchers from Brigham and Women’s Hospital (BWH) claim in a new study.
According to Carrie Gann of ABC News, this belief is known as the “hygiene hypothesis,” and suggests — in contrast to the common belief that people should strive to remain germ free regardless of circumstances — that bacteria and other germs may be “a necessary part of a healthy immune system, helping our body’s defenses beef up and fight future illnesses. When a person’s exposure to germs is decreased, problems may arise.”
In a press release detailing their findings, the BWH experts say that the hygiene hypothesis helps to explain the increase of allergic reactions and auto-immune diseases in cities throughout the world, and that medical professionals have claimed that various sociological and environmental changes, such as the use of antibiotics among younger patients, have contributed to this phenomenon.
However, no scientific study had ever discovered a biological basis for this belief. They say that their study, which was published Thursday in Science Express, changes that.
“The researchers show that in mice, exposure to microbes in early life can reduce the body’s inventory of invariant natural killer T (iNKT) cells, which help to fight infection but can also turn on the body, causing a range of disorders such as asthma or inflammatory bowel disease,” Nature‘s Helen Thompson reported on March 22.
The BWH researchers report that, after studying the immune systems of both “germ-free mice” and those who have received normal exposure to bacteria and other microbes, they discovered that the germ-free mice “had exaggerated inflammation of the lungs and colon resembling asthma and colitis, respectively.”
“Most importantly, the researchers discovered that exposing the germ-free mice to microbes during their first weeks of life, but not when exposed later in adult life, led to a normalized immune system and prevention of diseases,” they added. “Moreover, the protection provided by early-life exposure to microbes was long-lasting, as predicted by the hygiene hypothesis.”
The researchers warn that additional research is required to see whether or not the hypothesis holds true for humans as well, but according to Gann, experts claim that the biological mechanism analyzed in the mice during this study is similar in people.
Likewise, Erika Von Mutius, head of the Munich University Children’s Hospital Asthma and Allergy Department, told Nature that the findings “complement what we see in epidemiology… It supports the idea that the microbiome is very important and the age of exposure is decisive.”
