FCGR2A and infection: We found that infection of either K562 or THP-1 cells with SARS-CoV-2 pseudovirus yielded only background levels of luciferase activity (~18 units), whereas the same amount of pseudovirus produced very strong luciferase signals averaging 915,470 units on 293T-hACE2 cells (Supplementary Fig. 8a, b), suggesting that SARS-CoV-2 pseudovirus entry into the two FcγR-expressing cell lines was minimal.