TFRC and COVID-19: To address whether the entry of SARS-CoV-2 into monocytes and macrophages was mediated by receptors other than ACE2, we measured mRNA of previously reported SARS-CoV-2 receptors including BSG (encoding CD147), TFRC (encoding transferrin receptor-1), and NRP1 (encoding neuropilin-1) in CD14+ monocytes and MoAMs in COVID-19 lungs using scRNA-seq.31–34 We found that CD14+ Mono-1, -2, and MoAM-1, -2 expressed BSG, TFRC, and NRP1, but not ACE2 (Fig. 4g), suggesting that CD147, transferrin receptor-1, or neuropilin-1 might mediate SARS-CoV-2 infection of monocytes and macrophages.