PCNA and COVID-19: Compared to biopsies with hemolytic uremic syndrome (HUS) the kidneys of patients with COVID-19 (COV) showed significantly lower proliferative activity measured as PCNA positive area, which was comparably low to those of biopsies with acute tubular injury (ATI), disseminated intravascular coagulation (DIC) and in 1 year protocol biopsies that served as controls (Ctrl) (Figures 3A, C–G, green staining).