Getting the dirt on immunity: Study shows early exposure to germs is a good thing

(Medical Xpress) -- Previous human studies have suggested that early life exposure to microbes (i.e., germs) is an important determinant of adulthood sensitivity to allergic and autoimmune diseases such as hay fever, asthma and inflammatory bowel disease.

This concept of exposing people to germs at an early age (i.e., childhood) to build immunity is known as the hygiene hypothesis.

Medical professionals have suggested that the hygiene hypothesis explains the global increase of allergic and in urban settings. It has also been suggested that the hypothesis explains the changes that have occurred in society and , such as giving antibiotics early in life.

However, neither biologic support nor a mechanistic basis for the hypothesis has been directly demonstrated. Until now.

Researchers at Brigham and Women's Hospital (BWH) have conducted a study that provides evidence supporting the hygiene hypothesis, as well as a potential mechanism by which it might occur.

The study will be published online in the journal Science on the website on March 22, 2012.

The researchers studied the immune system of mice lacking bacteria or any other microbes ("germ-free mice") and compared them to mice living in a normal environment with microbes.

They found that germ-free mice had exaggerated inflammation of the lungs and colon resembling asthma and colitis, respectively. This was caused by the hyperactivity of a unique class of T cells () that had been previously linked to these disorders in both mice and humans.

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.

Moreover, the protection provided by early-life exposure to microbes was long-lasting, as predicted by the .

"These studies show the critical importance of proper immune conditioning by microbes during the earliest periods of life," said Richard Blumberg, MD, chief for the BWH Division of Gastroenterology, Hepatology and Endoscopy, and co-senior study author, in collaboration with Dennis Kasper, MD, director of BWH's Channing Laboratory and co-senior study author. "Also now knowing a potential mechanism will allow scientists to potentially identify the microbial factors important in determining protection from allergic and autoimmune diseases later in life."

In light of the findings, the researchers caution that further research is still needed in humans.

More information: www.sciencemag.org/content/ear… 3/21/science.1219328

Provided by Brigham and Women's Hospital

4.8 /5 (8 votes)

Related Stories

Study links 'hygiene hypothesis' to diabetes prevention

Oct 06, 2008

A research study funded by JDRF suggests that a common intestinal bacteria may provide some protection from developing type 1 diabetes. The findings provide an important step towards understanding how and why type 1 diabetes ...

Is cleanliness wiping out our immune system?

Jun 02, 2011

(Medical Xpress) -- Too much cleanliness has been linked to the alarming rise in auto-immune and allergic diseases in the Western world, says Professor Barbara Fazekas de St Groth from the Centenary Institute. But the answer ...

Gastric bacterium Helicobacter pylori protects against asthma

Jul 01, 2011

Infection with the gastric bacterium Helicobacter pylori provides reliable protection against allergy-induced asthma, immunologists from the University of Zurich have demonstrated in an animal model together with allergy specia ...

Study shows how flu infections may prevent asthma

Dec 13, 2010

In a paper that suggests a new strategy to prevent asthma, scientists at Children's Hospital Boston and their colleagues report that the influenza virus infection in young mice protected the mice as adults against the development ...

Recommended for you

Research reveals how lymph nodes expand during disease

22 hours ago

Cancer Research UK and UCL scientists have discovered that the same specialised immune cells that patrol the body and spot infections also trigger the expansion of immune organs called lymph nodes, according to a study published ...

Protecting us from our cells

Oct 22, 2014

Our immune system defends us from harmful bacteria and viruses, but, if left unchecked, the cells that destroy those invaders can turn on the body itself, causing auto-immune diseases like type-1 diabetes ...

User comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Telekinetic
not rated yet Mar 22, 2012
Granny always said- "Yer gonna eat a peck o' dirt afore ya die!"
alfie_null
not rated yet Mar 24, 2012
Kids are good at exposing themselves no matter what steps you've taken to present a sterile environment. Everything ends up in the mouth. My question regarding the mice: what does "exposed" mean? To what degree does being exposed mean getting sick? (vs. a little inflammation, no symptoms, etc.)