Early Exposure to Germs Could Help Build Immunity

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.”

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