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For almost three years, scientists have raced to understand the immune responses in patients who develop severe COVID-19, with an enormous effort aimed at defining where healthy immunity ends and destructive immunity begins.
In the early days of the COVID-19 pandemic, much attention focused on reports of harmful inflammation and so-called cytokine storms—dangerous immune overreactions that can lead to tissue damage and death—in patients with severe COVID-19. It wasn’t long before researchers began to identify antibodies that target the patient’s own body rather than attacking SARS-CoV-2, the virus that causes COVID-19.
Those studies revealed that patients with severe COVID-19 share some of the key traits of chronic autoimmune diseases—diseases in which the patient’s immune systems chronically attack their own tissues. Scientists have long suspected and sometimes even documented links between viral infection and chronic autoimmune diseases, but the research remains murky. However, the COVID-19 pandemic has offered an opportunity to better understand potential connections between these conditions.