Front-line health-care providers work with seriously ill COVID-19 patients in an intensive care unit at Barnes-Jewish Hospital in St. Louis. New research from scientists at Washington University School of Medicine suggests that the immune systems of such patients can’t do enough to protect them from the virus. The researchers are proposing that boosting the activity of immune cells may be a good treatment strategy for COVID-19. Credit: Matt Miller/School of Medicine

As the COVID-19 pandemic continues to claim lives around the world, much research has focused on the immune system’s role in patients who become seriously ill. A popular theory