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This is the VOA Special English Health Report.
A new study suggests that early exposure to germs strengthens the immune system. That means letting children get a little dirty might be good for their health later in life.
The study involved laboratory mice. It found that adult mice raised in a germ-free environment were more likely to develop allergies1, asthma2 and other autoimmune disorders4. There are more than eighty disorders where cells that normally defend the body instead attack tissues and organs.
They include rheumatoid arthritis5, which attacks the joints6; Crohn's disease, an inflammatory bowel7 condition; and juvenile8 diabetes9. Hay fever, a common allergy10, is also an autoimmune disorder3.
Richard Blumberg is a professor at Harvard Medical School in Boston, Massachusetts. He says in nineteen eighty-nine, medical researchers sought to explain these diseases with what they called the "hygiene11 hypothesis." They proposed that the increasing use of antibacterial soaps and other products, especially early in life, could weaken immune systems.
RICHARD BLUMBERG: "The hypothesis has stated or suggested that early-life exposure to microbes is a very important determinant of later life sensitivity to allergic12 and so-called autoimmune diseases, such as hay fever, asthma, inflammatory bowel disease and others."
Now, Dr. Blumberg and a team have what they say is the first biological evidence to link early exposure to germs to stronger adult immune systems. They say this exposure could prevent the development of some autoimmune diseases.
In the adult germ-free mice, they found that inflammation in the lungs and colon13 was caused by so-called killer14 T cells. These normally fight infection. But they became overactive and targeted healthy tissue -- an autoimmune condition seen in asthma and a disease called ulcerative colitis.
Dr. Blumberg says the mice raised in a normal environment did not have the same reaction. He says their immune systems had been "educated" by early exposure to germs.
RICHARD BLUMBERG: "What was really most remarkable15 to us was the fact that once the education event provided by the microbes occurred in early life, it was durable16 and lasted throughout the life of the animal."
Rates of autoimmune disorders are rising worldwide, but mostly in wealthier, industrialized countries.
RICHARD BLUMBERG: "I think one obvious question, for example, that’s raised by these studies is the early life use of antibiotics17 and whether we need to be more careful in their prescribing."
Rob Dunn is a professor of ecology and evolutionary18 biology at North Carolina State University in Raleigh. He says the new study does not mean people should stop washing.
ROB DUNN: "Wash your hands, but don't do it with antimicrobial soap. Let your kids play in a reasonable amount of dirt and get outside and get exposed to a diversity of things."
The study appears in the journal Science.
And that's the VOA Special English Health Report. I'm Steve Ember.
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1 allergies | |
n.[医]过敏症;[口]厌恶,反感;(对食物、花粉、虫咬等的)过敏症( allergy的名词复数 );变态反应,变应性 | |
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2 asthma | |
n.气喘病,哮喘病 | |
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3 disorder | |
n.紊乱,混乱;骚动,骚乱;疾病,失调 | |
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4 disorders | |
n.混乱( disorder的名词复数 );凌乱;骚乱;(身心、机能)失调 | |
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5 arthritis | |
n.关节炎 | |
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6 joints | |
接头( joint的名词复数 ); 关节; 公共场所(尤指价格低廉的饮食和娱乐场所) (非正式); 一块烤肉 (英式英语) | |
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7 bowel | |
n.肠(尤指人肠);内部,深处 | |
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8 juvenile | |
n.青少年,少年读物;adj.青少年的,幼稚的 | |
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9 diabetes | |
n.糖尿病 | |
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10 allergy | |
n.(因食物、药物等而引起的)过敏症 | |
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11 hygiene | |
n.健康法,卫生学 (a.hygienic) | |
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12 allergic | |
adj.过敏的,变态的 | |
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13 colon | |
n.冒号,结肠,直肠 | |
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14 killer | |
n.杀人者,杀人犯,杀手,屠杀者 | |
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15 remarkable | |
adj.显著的,异常的,非凡的,值得注意的 | |
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16 durable | |
adj.持久的,耐久的 | |
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17 antibiotics | |
n.(用作复数)抗生素;(用作单数)抗生物质的研究;抗生素,抗菌素( antibiotic的名词复数 ) | |
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18 evolutionary | |
adj.进化的;演化的,演变的;[生]进化论的 | |
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