A new study suggests that early exposure to germs __________ 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 __________, asthma and other autoimmune disorders. There are more than eighty disorders where cells that normally defend the body instead attack tissues and __________.
They include rheumatoid arthritis, which attacks the joints; Crohn’s disease, an inflammatory bowel condition; and juvenile diabetes. Hay fever, a common allergy, is also an autoimmune __________.
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 «hygiene hypothesis.» They proposed that the increasing use of __________ 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 __________ is a very important determinant of later life sensitivity to allergic and so-called autoimmune diseases, such as __________ 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 __________ the development of some autoimmune diseases.
In the adult germ-free mice, they found that inflammation in the lungs and colon was caused by so-called killer T cells. These normally fight __________. 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 __________. He says their immune systems had been «educated» by early exposure to germs.
RICHARD BLUMBERG: «What was really most remarkable to us was the fact that once the education event provided by the microbes occurred in early life, it was __________ and lasted throughout the life of the animal.»
Rates of autoimmune disorders are rising worldwide, but mostly in __________, industrialized countries.
RICHARD BLUMBERG: «I think one obvious question, for example, that’s raised by these studies is the early life use of antibiotics and whether we need to be more careful in their __________.»
Rob Dunn is a professor of ecology and evolutionary 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 __________ and get outside and get exposed to a diversity of things.»
The study appears in the journal Science.