The discovery of large numbers of rare cells in the lungs of asthmatics could pave the way for new treatments - good news for 400,000 sufferers here, writes Dick Ahlstrom.
An Irish doctor has helped to make important discoveries in our understanding of asthma and how it develops. He and colleagues have found high numbers of a very specific immune cell in the lungs of asthmatics, a finding that may open the way to new treatments.
Dr John Faul was recently appointed as consultant respiratory physician at the Asthma Research Centre in Connolly Hospital, Blanchardstown, Dublin. An Irish medical graduate, he was previously on the academic faculty at Stanford University School of Medicine in California, where he was involved in the asthma research.
He was joint first author in the study, which was published earlier this month in the prestigious New England Journal of Medicine.
He returned to Connolly because of the high standard of research on the disease being done there. "We hope to expand on the earlier work," he says, in collaboration with researchers in Harvard and Stanford medical schools and in Perth, Australia.
Asthma is very prevalent in Ireland. There are an estimated 400,000 sufferers here, according to the Asthma Society of Ireland. International studies have also shown that we have the highest incidence of the disease in the world among those aged between 18 and 44 and the fourth highest incidence among children - behind Britain, Australia and New Zealand. As many as 29 per cent of children here are affected by asthma to some degree.
One of the key findings of the study is that asthma has a significant but little understood immune system connection related to a specific cell type known as "invariant natural killer T cells".
"What we found is that even though we usually think of asthma as driven by an allergic response, there is also a large component linked to latent immunity," explains Dr Faul.
Asthmatics react to a range of allergens including dust, house mites, animal dander and smoke and much research is focused on how allergens trigger asthmatic attacks. Dr Faul and his collaborators decided to study the immune system's part in the disease, given that so many different allergens could provoke an attack.
Our immune defences are meant to protect us against bacteria, viruses and toxins, and we have evolved two distinct immune responses - specific immunity and innate immunity. The former depends on antibodies which "remember" invading microbes and destroy them.
The latter system is far more ancient and provides an immediate response based on dendritic cells. These become activated if they encounter microbes and immediately begin recruiting immune system cells such as the T cells, which in turn release more signalling proteins that bring still more cells into the defence.
"They are two completely different kinds of defence mechanisms," says Dr Faul, yet his group discovered that there are unexpected connections between the two in people with asthma. This link is the invariant natural killer T cell.
While researchers knew that asthma produced an inflammatory process that attracts large numbers of immune cells into the lungs, Dr Faul and his group identified this new subgroup of T cells.
They are an extremely rare cell type, says Faul, making up just 0.01 per cent of immune cells in the bloodstream. Yet Dr Faul and his collaborators found them congregating in large numbers in the lung tissue of asthmatics.
"It is uniquely in asthma that more than 60 per cent of the cells in the lungs are these cells," says Faul. They were not seen in people who do not have asthma.
"For the first time we have found this target that is unique to asthma," he says. "This is the start of a fresh search for new therapeutic targets."
Dr Faul believes that the dendritic cells could be important in this process. "We think [invariant natural killer T cells] are recruited by the dendritic cells," he says, but researchers don't understand the process that brings so many of these rare cell types into the lungs.
"We want to learn how dendritic cells are recruiting or controlling the T cells," he adds. This is the new research target he plans to pursue.