BOSTON -- Research done at Boston's Children's Hospital pinpointed the cells responsible for causing asthma -- the disease that affects more than 20 million Americans.

Boston television station WCVB reported that the new development is not a cure, but medical researchers see it as a significant step in understanding the lung disease that sends more than 2 million people to the emergency room each year.

"We believe this is a totally new way to look at asthma," Children's Hospital Boston's Dr. Dale Umetsu said. "We found that asthma is caused not by T helper 2 cells, as had been thought in the past, but rather NKT cells, or natural killer T cells."

Scientists said that they were actually surprised by the findings. The NKT cells are found in other parts of the body, but the asthma breakthrough, published Wednesday in the New England Journal of Medicine, shows that when they enter the lungs, asthma occurs.

"These cells are extremely important in combating diseases such as cancer, but what we found was that they get recruited into the lungs, and this causes dysfunction, and this causes disease," Children's Hospital Boston's Dr. Omid Akbari said.

Asthma affects more than 20 million Americans. Almost half of them are 18 years old or younger. The disease has a great impact on society, too, with more than 12.8 million school days lost and 24.5 million adult workdays lost each year.

NKT cells were first found to cause asthma in mice, but it took more time for the human breakthrough.

"Because we didn't have the right tools. The tools to study those cells just came into our hands, like, a couple of years ago," Akbari said.

"At the moment, unfortunately, there really are no therapies for asthma that can eliminate or reduce NKT cells in the lungs of the patients with asthma," Umetsu said.

Umetsu hopes now that they know what cells cause asthma, a cure will come in the next five to 10 years.