ACE2 and COVID-19: To test if gene upregulation resulted in the secretion of cytokines that could contribute to the spread of pro-inflammatory signals, we compared the levels of secreted cytokines from infected Calu-3 or A549-ACE2 cells to cytokine levels in serum taken from infected patients with severe COVID-19 (Fig. 2c, d and Supplementary Fig. 2a, c).