Shedding light on the immune system’s role in severe COVID-19

In a new study, researchers from SciLifeLab, Karolinska Institutet and Helsinki University, have investigated immune cell activation in patients with severe COVID-19 infection. Several cell types, playing a key role in the hyperinflammation seen in these severe cases, were identified.

“These findings are valuable in improving the clinical evaluation of patients and in the development of new treatments that modulate and mitigate the overreaction of the immune system in patients with severe COVID-19,” says senior author Petter Brodin (SciLifeLab/Karolinska Institutet), in a press release from Karolinska Institutet.

In the study, published in the scientific journal Cell Reports, samples taken from patients with severe COVID-19 treated in Helsinki, Finland, were analyzed. Using advanced techniques , such as mass cytometry, the entire composition and function of the immune system was investigated and up to 14 repeated blood samples were taken from each patient.

“This has enabled us to make an unusually detailed analysis of immune system activation during severe COVID-19, and we have described several new details of immune system response to the virus and its hyperresponsiveness in severely ill patients,” says Petter Brodin.

The results revealed that eosinophils – white blood cells normally associated with asthma and parasitic infections – play an important role in severe COVID-19 infections. These cells expand in the blood just before the patients suffer a deterioration in health due to pulmonary hyperinflammation, and ARDS (acute respiratory distress syndrome).

Another type of immune cells called basophils seem to be involved in the development of a strong antibody response during the infection, according to the study.

The researchers have also mapped how the immune system recovers in patients who have recovered from severe COVID-19.