Researchers in France have discovered that patients suffering from severe COVID-19 show changes in a class of immune cells known as unconventional T cells. The study, published today in the Journal of Experimental Medicine (JEM), suggests that monitoring the activity of these cells in the blood of patients could predict the severity and course of the disease.

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While most people infected with the SARS-CoV-2 virus experience relatively mild symptoms, some patients mount an aberrant inflammatory response that can damage the lungs and cause acute respiratory distress syndrome (ARDS), potentially resulting in the patient’s death. However, the immune cells and inflammatory molecules responsible for ARDS associated with COVID-19 remain unclear.

Unconventional T cells are a diverse class of immune cells that help control the response to viral infection and are commonly found in the lungs and other mucosal tissues in the body. “Despite this, the role of unconventional T cells in the pathophysiological process of SARS-CoV-2–driven ARDS has not yet been explored,” says Christophe Paget, a researcher at the INSERM Research Center for Respiratory Diseases, University of Tours.