PSMB9 and COVID-19: For the NK cells, many ISGs were upregulated by STAT1 in severe COVID-19, such as EIF2AK2, PARP14, ISG15, PSMB9, MX1, SP110, DDX60, SAMD9L, ADAR, IFI44L, IFIT3, EPSTI1, SAMD9 (Supplementary Figure 6).