Researchers find link between flu, asthma

BOSTON — Researchers at Children's Hospital Boston have discovered the reason why influenza may induce asthma attacks among children.

A team led by senior investigator Dale Umets found that the flu can activate a newly recognized group of immune cells called natural helper cells, which prompts asthma attacks to occur. An infection, the team found, stimulates production of a compound called IL-33, which activates natural helper cells, which in turn secrete asthma-inducing compounds.

This discovery also may imply that existing asthma medications aren't effective enough, especially when a child is diagnosed with the flu or some other viral infection.

"Virtually 100% of asthmatics get worse with a viral infection," Umetsu said. "We really didn't know how that happened, but now we have an explanation, at least for influenza. Without these cells being activated, infection did not cause airway hyperreactivity, the cardinal feature of asthma. Now we can start to think of this [biological] pathway as a target, IL-33, the natural helper cell itself or the factors it produces."

The findings were published in the journal Nature Immunology.