Autoantibody reactivity implicated in 'long' COVID-19. Researchers at Yale University found that "friendly fire" from the immune system may account for severe disease in patients with COVID-19 and persistence of symptoms over time in those with "long COVID." The researchers (in a study available as a medRxiv reprint) examined blood samples from 194 COVID-19 patients with a range of severity over a two-month period and compared them with blood samples from 30 healthy people who had negative COVID-19 tests. They found "dramatic increases" in autoantibody reactivity across a wide range of immunological targets in the COVID-19 patients compared with the controls. None of the COVID-19 patients had COVID-19-specific autoantibodies, but rather a highly diverse range of uncommon or rare autoantibody reactivities, a possible explanation for the wide variation in patients' clinical responses to the virus. According to the researchers, the results indicate that autoantibodies are capable of affecting the clinical course of COVID-19 by "perturbing the immune response . . . and causing direct tissue injury."