Although there is no cure for asthma, researchers may be one step closer to combating this common and deadly illness.
According to a new study from the University Health System, exposure to cats may lead to a decreased risk of developing asthma. This is the first finding to date that implies that high exposure to a particular allergen leads to tolerance that can reduce or eliminate asthma responses in humans.
The research found a modified response, dubbed a Th2 response, which "explains a great deal of what is happening in allergy," said Thomas Platts-Mills, a professor of internal medicine and microbiology, and the lead investigator of the study.
The modified Th2 response is a pathway of immune system response to cat allergen, said Judith Woodfolk, an assistant professor of research for internal medicine and allergy, and a co-author of the research.
With this information, researchers may be able to create immune therapy to treat asthma.
"Inducing this tolerant response to cat allergen would provide an alternative immunotherapeutic strategy to treatments currently available," Woodfolk said.
Previous asthma treatments have focused on reducing allergen stimuli in the home. To combat asthma, the treatments have targeted three main proteins - cat, dust-mite and cockroach allergens, Platts-Mills said.
Although asthma patients are not necessarily allergic, "most children who develop or have asthma at age 13 are allergic to these stimuli," he said.
Past research has shown increased exposure to mite allergen induce asthmatic symptoms. Cat allergen, like all allergens, stimulate the body to produce antibodies.
But the study revealed that these antibodies did not cause asthmatic symptoms.
"Children that are living in a house with a cat and making these non-allergy forming antibodies are not at risk for asthma," Platts-Mills said.
Between 10 to 20 percent of children are within this tolerant range. These findings are evidence that pet cats can actually decrease the risk of asthma.
Incidences of asthma - the leading cause of chronic illness in children - have increased more than 75 percent in school-aged children over the past 15 years. According to the Asthma and Allergy Foundation of America, asthma is the only chronic disease other than AIDS and tuberculosis with an increasing death rate.
Each day, 14 Americans die from asthma. Asthma is also the leading cause of school absences, resulting in an annual loss of more than 10 million school days per year.
"Asthma has become incredibly common," Platts-Mills said. "Six to 10 percent of children have an inhaler."
The study
The study, published last month in the medical journal The Lancet, included results from 227 children in seventh and eighth grades from three middle schools. All students were screened for symptoms or a history of asthma.
The schools, located in Los Alamos, N.M., Albemarle County and Charlottesville, represented a wide range of climatic and socioeconomic conditions, Platts-Mills said.
"We wanted to see if there was a real difference in asthma among the various locations tested," he said. "We had a very wide range of domestic exposures to the children."
The children were given skin tests and histamine to determine each child's level of allergic response. The researchers also collected dust samples from each child's home. Their immune system response was compared to the amount of exposure to cat allergens in their home and to their history of asthma.
Other allergen studies
The study did not address the optimal period in which children should be exposed to cats. While other ongoing studies suggest the exposure should happen when children are young, Platts-Mills said it can occur at any time during childhood.
A long-term study in Boston is examining 400 children to show if producing non-allergy antibodies early decreases their risk of becoming allergic. "We are essentially asking the same question but looking at it sequentially," Platts-Mills said.
Another study in Sweden involves collecting 800 blood samples from children to see if cat allergen tolerance affects immune responses to dog allergen.
Platts-Mills' findings, however, may suggest that children can produce asthmatic symptoms if exposed to low levels of cat allergens.
For example, a person is very likely to become allergic to a neighbor's cat. This indirect exposure can elicit an immune response without building tolerance, Woodfolk said.
"Getting rid of the cat in order to prevent development of allergic disease may not be the appropriate strategy in a community where cat ownership is high," he said. "Levels of cat allergen in houses without a cat may still be sufficient to put children at risk of developing allergic disease."
In those situations, it might be helpful to keep a pet cat. Platts-Mills admitted that, as a result of the study's findings, he changed his position on cats.
"I am no longer taking a position against cats," he said. "The conclusion that cats are responsible for the increase in asthma is nonsense"
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