What can phlegm tell us about severe asthma?

What’s the role of white blood cells in asthma?

Asthma is a lung condition that involves uncontrolled inflammation in the airways which affects your breathing. It can make your airways smaller and cause symptoms like coughing, wheezing and shortness of breath. In some types of asthma, this inflammation is driven by a type of white blood cell called eosinophils. Eosinophils are an important part of the immune system, and we need them to keep us healthy.

But having too many of these cells in your airways for too long results in harmful inflammation. This kind of asthma is often treated with medicine called biologics that help reduce the number of eosinophils and block the harmful inflammation they cause. However, when patients with this type of asthma are treated with biologic injections, only 3 out of 10 people have an excellent response to them, suggesting there are other factors we need to address.

Why might biologics not work for some people with severe asthma?

Our previous work has shown that some patients with asthma caused by eosinophils also have more inflammation caused by another type of white blood cell called neutrophils. Neutrophils are a key part of your immune system that helps fight infections and heal injuries. We also found that some of these patients also have higher levels of certain types of bacteria in their airways. The injections that block the inflammation caused by eosinophils don’t block these other pathways of increased inflammation and so these patients don’t respond as well to these treatments. 

What happens when our body can’t control inflammation?

Inflammation is our immune system’s response to injury or infection. But when this inflammation is uncontrolled, it can cause damage. Our bodies have ways to protect itself from the inflammation caused by our immune system’s response. But in some people with lung conditions such as bronchiectasis and cystic fibrosis, research has shown that they have lost some of these protective processes. Without this help to control the increase in our immune system activity, the resulting inflammation can damage our airways. We’re looking at whether people with severe asthma also show similar loss of protection.

Why is looking at phlegm in severe asthma important?

We’re using existing samples of phlegm (a mix of saliva and mucus that you cough up), also known as sputum, collected in clinical studies to see if there are different levels of protective mechanisms in place in different asthma patients. We would also like see if there’s any difference in the body’s defence mechanisms before and after commencing biologic treatment, and if there’s any difference in the body’s defence mechanisms during an asthma attack compared to when asthma is stable.

What impact will this research have on people with severe asthma?

Gaining a greater understanding of the role that different types of inflammation play in different asthma patients helps to guide our research to test how we can best manage inflammation in the airways of asthmatics to improve their symptoms and protect their lung health in the future.  Understanding if some patients may have a loss of airway defence mechanisms and understanding if these defence mechanisms vary at different times - such as during an asthma attack - can help us find ways to reduce the damage to the airways caused by over-active immune system responses. 

While biologic treatments have changed the lives of many people who live with severe asthma, they don’t make asthma patients better, and severe asthma can still be very distressing and debilitating. But breakthroughs like this could be transformative, creating new treatments that help more people with severe asthma to live longer, healthier lives.