C3 and COVID-19: HEP6 and HEP7 cells had similar profiles to those in the HEP2 subset but with high expression of acute phase proteins in HEP7 (e.g., CRP, C3, C4a, SAA1, and FTH1; a COVID-19 specific cluster; below) or apoptosis and cellular senescence pathways in HEP6 (Fig. 3b, Additional file 2: Fig. S3a).