ACE2 and COVID-19: CD147 is expressed on various types of proinflammatory cells including Th17 cells, neutrophils, NK cells,48,49 where ACE2 is rarely expressed.50 Thus, SARS-CoV-2-infected hCD147 transgenic mice well recapitulate the symptoms of COVID-19 pneumonia, providing a good model for studying the pathogenic mechanism and pharmacodynamics of agents against COVID-19.