New research explains severe viral attacks on lungs

London: A team of Swedish researchers has revealed how different types of immune cells, called macrophages, grow in the lungs, and which of them could be the cause of serious lung disease, a finding that could contribute to future treatments for Covid -19, among other diseases.

To date, research on the development of human pulmonary macrophages has been limited.

In a new study published in Immunity, researchers at Karolinska Institutet in Sweden used a model to study the development of pulmonary macrophages directly in a living lung.

This was combined with a method to study gene activity in individual cells, RNA sequencing, and thus discovered how blood monocytes become human lung macrophages.

“In our study, we show that classical monocytes migrate through the airways and lung tissue and are converted into macrophages that protect lung health and function,” said Tim Willinger, associate professor in the department of medicine who led study.

“We have also identified a particular type of monocyte, HLA-DRhi, which is an immune cell intermediate between a blood monocyte and an airway macrophage.”

These HLA-DRhi monocytes can leave the bloodstream and migrate into lung tissue.

Macrophages are immune cells that, among other things, protect the lungs from such attacks.

But under certain conditions, pulmonary macrophages can also contribute to serious lung diseases, such as chronic obstructive pulmonary disease (COPD) and Covid-19.

However, unclassical monocytes grow into macrophages in the many blood vessels of the lungs and do not migrate into lung tissue.

In an infection with the new coronavirus, SARS-COV-2, which causes Covid-19, researchers believe that protective and anti-inflammatory macrophages are replaced by pro-inflammatory pulmonary macrophages of blood monocytes.

“Given their important role in rapid inflammatory responses, our results indicate that future treatments should focus on inflammatory macrophages and monocytes to reduce lung damage and mortality from severe Covid-19,” said Willinger.