by - Alan Mozes
Updated: Jul 1st 2010

THURSDAY, July 1 (HealthDay News) -- People with asthma appear to have subtle differences in a gene that encodes a protein responsible for deciding whether particular immune cells live or die, new research reveals.

A Johns Hopkins team examined the gene controlling the protein -- known as Siglec-8 -- by analyzing DNA samples taken from nearly 1,000 adults and children, half of whom had asthma and have of whom did not.

All the samples were taken from African-American individuals who had participated in a group of U.S. National Institute of Health studies called the Genomic Research on Asthma in the African Diaspora.

The team found that a single genetic code mutation in Siglec-8 -- an abnormality called rs36498 -- appears to be linked to a higher risk for asthma.

The observation was reinforced by further DNA analyses conducted with samples taken from both Brazilian and Japanese patients.

The John Hopkins team, led by Dr. Bruce S. Bochner, director of the division of allergy and clinical immunology, has studied the protein Siglec-8 for almost a decade.

The protein is found on the surface of several types of immune cells that play different but cooperative roles. When operating normally, each cell helps prevent infection and keep the body healthy. But when confronted by allergic reactions and asthma attacks, Bochner and his colleagues have noted, these cells can respond so forcefully that they can actually cause more harm than good.

The researchers speculated that mutations in the Siglec-8 gene might cause certain individuals to end up with extra eosinophils -- white blood cells that, along with mast cells, are involved in asthma and allergies -- and thus be more susceptible to developing the disease.

"Our results suggest these mutations in the Siglec-8 gene may play a role in asthma," said Bochner. "If were able to understand these mutations better we might be able to use them to develop a diagnostic test or new treatment."

The finding is reported in the June issue of The European Journal of Human Genetics.

More information

For more on asthma visit the U.S. National Heart Lung and Blood Institute.

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