The cause for severe asthma has been identified by researchers at the Cincinnati Children's Hospital Medical Center, who had used mice in their study.
The disease can be triggered in susceptible people by a variety of environmental contaminants - such as cigarette smoke, allergens and airborne pollution.
Dr. Marsha Wills-Karp and her colleagues have identified the pro-inflammatory protein, interleukin-17 (IL-17A), as the molecular tipping point that upsets a delicate balance between underlying mild disease and more severe asthma, reports Nature.
Airway exposure to environmental allergens causes dysfunctional regulation of a gene called complement factor 3 (C3). This leads to overzealous production of IL-17A by airway cells and sets off what the scientists describe as an "amplification loop," when IL-17A in turn induces more C3 production at the airway surface.
The amplification loop perpetuates increasing inflammatory responses as well as airway hyper-responsiveness and airflow obstruction.
As the team continues their research, they will study the relationship between C3 and IL-17A in severe asthmatics, and explore the effectiveness of targeting either the C3 or IL-17A pathways for the treatment of severe asthma.
The study is published in the latest Nature Immunology.