Around one in 10 asthmatics has the severe form of the disease, which frequently requires progressively higher doses of steroids in a bid to control symptoms.
Severe asthma is also associated with a much higher risk of illness and death than milder forms and accounts for almost a third of health service costs for asthma
The research team investigated tumour necrosis factor alpha (TNF alpha), which is found in a range of chronic inflammatory conditions, including rheumatoid arthritis, Crohn's disease, and psoriasis.
Included in the study were 26 healthy people, 67 mild asthmatics, and 51 severe asthmatics. Bronchial fluid and lung tissue samples were taken from the participants to discover their levels of TNF alpha.
Levels were significantly higher in those with severe disease and concentrated in one particular type of immune cell (mast cells) which are recognised components of the inflammatory reaction in asthma.
TNF alpha levels were low and similar in those with no asthma or who only had mild symptoms.
This suggests that the high levels of TNF alpha in severe disease are characteristic of more chronic disease that is resistant to steroid treatment, rather than a feature of the disease itself, say the authors.
Seventeen people with severe asthma who still had symptoms, despite being treated with a range of drugs, were also given 25 mg of a drug that blocks TNF alpha production (etanercept) twice weekly, injected below the skin for 12 weeks. Fifteen completed the course.
At the end of the study period, these patients experienced a significant improvement in symptoms and lung function. Two patients were able to discontinue one of their drugs.
The treatment also curbed the inflammatory reaction in the lungs, known as bronchial hyperresponsiveness. And there were few side effects.
The authors caution that further research will be required before this approach can be recommended, but they say that it offers a potentially new avenue of treatment for severe asthma.