PROS1 and COVID-19: SARS-CoV-2 S protein binds to ACE2, induces defects in human HPC colony-forming ability and inhibits the expansion of HSC and HPC subpopulations in vitro.400 In addition, in human very small embryonic stem cells (VSELs) and HSCs, the interaction of ACE2 with S protein activates the NLRP3 inflammasome, which may cause cell pyrolysis.401 The plasma of severe COVID-19 patients induces HPC to produce suppressive bone marrow cells in vitro, in relation to the high levels of IL-6 and IL-10 in plasma.402