Posted on 03/17/2006 7:14:02 AM PST by SheLion
WEDNESDAY, March 15 (HealthDay News) -- As medical technologies improve, researchers are rooting out more information about possible causes of common diseases, such as asthma.
One new finding, reported in the March 16 issue of the New England Journal of Medicine, is that immune system cells long thought to cause asthma may not be the primary culprit behind the disease.
"We found that asthma is caused not by T-helper 2 cells as has been previously thought, but by a novel class of cells called natural killer T cells," said one of the study's authors, Dr. Dale Umetsu, a professor of pediatrics at Harvard Medical School and Children's Hospital Boston, and a visiting professor at Stanford University in California.
"The majority of T cells in people with asthma aren't what we thought they were," he added.
According to Umetsu, natural killer T cells were only recently discovered because the technology to differentiate these cells from others hasn't been around long.
T cells are a part of the body's immune defenses and normally help rid the body of foreign invaders, such as viruses or bacteria. In asthma, however, the immune cells don't work as they should and instead produce inflammation in the lungs.
More than 20 million Americans have been diagnosed with asthma, according to the U.S. Centers for Disease Control and Prevention, and about 4,200 people die from the disease each year.
Asthma symptoms include wheezing, coughing, breathing difficulties and a feeling of tightness in the chest. While the exact cause of the disease is unknown, doctors do know that asthma can be exacerbated by exposure to certain triggers, such as dust mites, pollen, pets and even exercise or cold air. There is no cure for asthma, only treatments aimed at managing it.
Because studies in mice uncovered the presence of natural killer T cells only in rodents with asthma, the researchers behind the new study compared samples from 14 people with asthma to samples from six healthy "controls" and five people with another inflammatory lung disorder called sarcoidosis, which is unrelated to asthma.
About 60 percent of the T cells in the asthma group were natural killer T cells, not the expected helper T cells. No natural killer T cells were evident in samples from the healthy control group or the people with sarcoidosis.
"These were very surprising findings -- a turn of events that no one suspected in the past," said Umetsu. "Part of the reason they escaped notice is they have many features that are similar to T helper 2 cells. Now, we need to know more about the biology of natural killer T cells to develop more specific therapies for asthma."
"None of the current [asthma] therapies are focused on targeting natural killer T cells. Perhaps as we develop therapies that can eliminate them from the lungs, we could have more effective and possibly curative therapies for asthma," he said.
The first step, however, is to confirm these findings in a larger group of people, and in a more diverse population of people with asthma, because there are different types of asthma. Some people have asthma that's triggered by allergens, while for others exercise or cold air can induce airway spasms.
Also, Umetsu said that researchers have to learn more about how these cells work and what causes them to go to the lungs initially. Natural killer T cells appear to respond to different things than helper T cells.
Any potential therapy would have to specifically target the lungs because natural killer T cells do have some protective effects in the rest of the body, he added.
Dr. Jonathan Field, director of the allergy and asthma clinic at New York University Medical Center/Bellevue in New York City, said, "This may be a new paradigm of how people develop asthma."
But, he cautioned that more needs to be learned about these cells, such as whether they are the actual cause of disease or if they simply appear in response to the disease.
"You have to wonder which [immune cells] actually are causing the most pathology," Field said. "Are natural killer T cells causing the changes? Which cell is the conductor and which is the actual locomotive?"
Sounds like asthma needs to be reclassified as an autoimmune disease.
"In our study, wintertime air pollution had no significant effect on asthma exacerbations or lung function," said Nathan Rabinovitch, M.D., a lead author of the study and pediatric allergist at National Jewish Medical and Research Center. "Upper respiratory infections, however, doubled the chances that a child would suffer an asthma exacerbation and more than quadrupled the odds that a child would suffer asthma symptoms."
The study monitored 41, 63 and 43 elementary school children during three successive winters in Denver, Colorado, when particulate pollution is worst. The children, aged 6 to 12 years, were mostly urban minority children with moderate to severe asthma. Dr. Rabinovitch and co-investigator Erwin Gelfand, M.D., Chairman of Pediatrics at National Jewish, monitored several health outcomes in the children, including asthma exacerbations, visits to emergency rooms and hospitalizations. They also monitored the children's lung function, medication use, asthma symptoms, and whether they had upper respiratory infections.
The researchers correlated those health measures with daily variations in six air pollutants: particulates less than 10 microns in diameter, particulates less than 2.5 microns diameter, carbon monoxide, nitrogen dioxide, sulfur dioxide and ozone. In general pollutants were comparable to levels found in most large American cities.
As expected, the raw data did show worse health associated with high pollution days. But when the researchers controlled for potential time-related confounders, such as upper respiratory infections, the correlation disappeared on almost all measures. Higher carbon monoxide levels were marginally associated with increased use of rescue medications (odds ratio: 1.065) and daily symptoms were marginally associated with ozone levels (odds ratio: 1.083).
"It is well known that upper respiratory infections can cause problems for people with asthma, but the air pollutions results were a surprise," said Dr. Gelfand. "We believe that careful monitoring of the children allowed us to filter out confounding factors that would have mistakenly suggested a significant health impact of air pollution."
The researchers are not ready to write off the effects of air pollution during summer. For one, children may be exposed to higher levels of air pollution in the summer because they spend more time outside. Also, ozone, a known respiratory irritant, rises to much higher levels during the summer and may pose more of a problem than particulate pollution in the winter. Next summer Drs. Rabinovitch and Gelfand will begin a study of the health impacts of ozone on children with asthma.
"We believe this is good news for parents of children with asthma," said Rabinovitch. "Instead of worrying about air pollution they can focus their efforts on preventing and treating the real wintertime threat to their children's health - colds and other respiratory infections."
http://www.nationaljewish.org/news/particle_pollution_rabinovitch.html
November 9, 2004
I'm not sure what is going on here. Times have changed yet asthma is getting worse. Scary.
Yes....and autoimmune disorders like rheumatoid arthritis, multiple sclerosis and lupus are reaching near epidemic proportions......scary, indeed.
Not quite - autoimmune would suggest self-recognition by immunoglobulins. This is more a defect in the T cells in which they produce an inflammatory response where one is not needed or wanted.
As a mild Asthma sufferer...... HURRAY!!! Progress being made!
What, no jibber-jabber about tobacco being a "cause" of asthma in either article?
I developed asthma in my 40's. Cold air was the number one trigger for me but eventually I was short of breath nearly round the clock. I was treated by my primary care physician but I felt I was getting worse...sucking on that albuterol canister all day.
I went to an allergist who discovered that the only allergies I had were to cats,which I knew, and oak. He took me off all of the meds my Dr. had prescribed and gave me Pulmicort. I feel as though I am asthma fee. Not a single episode in over a year and I have never opened my albuterol prescription since it's last refill in July.
The allergist is stunned by my progrss. According to him my lung function is nearly 100%. Can you outgrow adult onset asthma?
And not mentioned as one of the "triggers" either.
What "trigger" metesky??
OH YES! You noticed that too? Nope. Not one peep about smoking and/or second hand smoke.
The allergist is stunned by my progrss. According to him my lung function is nearly 100%. Can you outgrow adult onset asthma?
Wow! Good for YOU!! I bet you feel wonderful!!!
"Pulmicort." I haven't heard of it. Is it a pill form?
I sure don't know if you can outgrow asthma or not. But they say with medications, you can manage it. I bet you are really relieved.
Horsefeathers. Chemicals have been in everything since the beginning of time.
The incidence of most "cancers" is on the decline not increase.
It is a dry powder inhaler that delivers budesonide, a high-potency corticosteroid that has shown to be a powerful inhibitor of airway inflammation. It is $$$. Must be used every day and not for acute attacks.
You do not have "adult-onset" asthma but an extrinsic asthma brought on by the cats allergens. I cannot get rid of my daughter's cat so i will suffer for a few more years (the cat always finds its way back to the house...>1 mile and counting).
If you can get rid of the cat your asthma should go away.
Oak? That's interesting. Just the bare wood, furniture, leaves or sap?
Oak is also a wood that horses don't like to chew on. Putting some in my new horse barn as trim.
Pulmicort is an inhaler. And you bet I'm relieved. I had reached the point where I was uneasy about travel. The thought of being on a plane and possibly having an episode was terrifying.
I have to remind myself every day not to leave the house with my rescue inhaler ,just in case.
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