A study has found abnormal immune cells in the lungs of patients with persistent breathlessness months after a Covid-19 infection.
The altered immune cells in the airways are thought to cause ongoing lung damage.
The research was undertaken by scientists at Imperial College London and involved people who had been previously hospitalised with Covid-19. The findings, published in Immunity, suggest that recovery from Covid-19 infection might be accelerated by treatments that dampen the immune system and reduce inflammation.
Professor Pallav Shah, a joint senior author of the study from Imperial College, said: ‘These findings suggest that persistent breathlessness in our group of Covid-19 patients is being caused by failure to turn off the immune response, which leads to airway inflammation and injury.’
To examine the causes of post-Covid breathlessness, the researchers studied CT scans of the lungs of 38 patients three to six months after they left hospital and compared them against 29 healthy volunteers who had not had Covid-19. Fluid samples from the lungs were also examined to determine which immune cells were active in the airways, as well as looking at markers in the blood.
The participants who had suffered with Covid-19 were found to have more immune cells in their lungs in comparison to those who had not been infected. However, there was no difference in the immune cells seen in the blood in either group.
Co-author, Dr Bavithra Vijayakumar, from Imperial College explained that other studies found an increase in various types of immune cells in both the blood and the lungs as an immediate response to Covid-19 infection, but this new research has shown that this changed a few months later.
She said, ‘After three to six months, it appears that these signs in the blood return to normal, while those in the lungs take longer to resolve. Our finding that the immune response in the blood doesn’t appear to match that of the lungs emphasises the importance of assessing airway immunity in order to better understand persistent respiratory symptoms post Covid-19.’
Although the immune cells in the lungs varied for each post-Covid-19 patient, they all tended to have higher levels of immune cells linked to cell death, epithelial damage and tissue repair.
Professor Shah added: ‘The next steps of our research will be to see if there are treatments that can reduce the immune activity and whether they help to reduce the persistent breathlessness some patients experience.’
The study comes after a study last month found people fully vaccinated against Covid-19 are around half as likely to develop long Covid symptoms as unvaccinated people or those who had only received one vaccine dose.