The reddish coloration in these lung stem cells marks proteins that play an important role in late sequelae after infection with the coronavirus or other viral pathogens. Because they cause the cells to proliferate excessively.
After an infection with the coronavirus or other viruses, changes in the lungs often remain. Lung cells grow increasingly into the thin space between the air-filled alveoli and the blood vessels and impede gas exchange. In addition, there may be an increased formation of mucous glands that produce disruptive mucus. The consequences are breathing difficulties that sometimes last for months after a Covid 19 disease and a reduced supply of oxygen to the blood. In the case of other viral pathogens, such as an infection with the respiratory syncytial virus in childhood, this can lead to an increased tendency to develop asthma.
Researchers working with Michael Holtzman from Washington University in St. Louis have discovered what is behind this. Through infection experiments with mice, among others, they found that the virus infection in the lung tissue triggers the release of the signal protein interleukin-33. This protein can be recognized by its reddish color in this image of basal lung stem cells.
Interleukin-33 normally ensures that stem cells are stimulated to grow and repair tissue damage. But in the case of Covid-19 and other respiratory virus infections, this reaction is excessive and becomes a problem. This is because the stem cells migrate into the tissue of the alveoli and produce more new cells there than they should. This thickens the tissue, stimulates mucus production and attracts immune cells that cause inflammation in the tissue.
The positive, however: the elucidation of these processes and the role of interleukin-33 could now help to develop new therapies against the long-term effects of viral respiratory infections.