Researchers at Korea Advanced Institute of Science and Technology (KAIST) have found a biomarker that helps differentiate severe and mild Covid-19 patients quickly, the institute said Monday.

Covid-19 has very different symptoms depending on the patients. To predict and differentiate a patient's severity, it is important to use biomarkers and select a targeted therapy that can treat them, the institute said.

The team, led by Professor Lee Heung-kyu, discovered a factor that determines the severity of Covid-19 by revealing the association between neutrophils and glucocorticoids.

The researchers analyzed the single-cell genetic information present in the bronchial alveolar lavage fluid of mild and severe patients with Covid-19 infection. They found that severe Covid-19 occurred due to the over-activation of neutrophils, the importance of which had been relatively unknown during viral infection.

Particularly, they discovered that neutrophil influx increased due to chemokine, such as CXCL8, expressed in bone marrow-derived immune cells such as macrophages.

"We found that the production of CXCL8 is regulated by the expression of glucocorticoid receptors in immune cells derived from bone marrow, which is consequently associated with the influx and activity of neutrophils," the institute said.

Professor Lee also said, "This study has led us to discover a biomarker that determines the severity of Covid-19 and to begin to develop a treatment that will ease its severity by making the most of glucocorticoid inhibitors."

The journal Frontiers in Immunology published the results of the study in its August issue.