ACE2 and COVID-19: Multiple recent studies have documented the upregulation of autoantibodies such as antibodies to ACE2, anti-nuclear autoantibodies, and immunomodulatory factors (including complement components, chemokines, cytokines, and cell-surface proteins) in patients with persistent symptoms following SARS-CoV-2 infection.120,121,190–192 An observational study indicated that the upregulation of IgG antibodies against ACE2 was found in 1.5% of patients with COVID-19,191 implying the widespread existence of autoantibodies to ACE2.