Compared to ciliated cells from control WHO 0 participants, cells from both mild/moderate and severe COVID-19 upregulated genes involved in the host response to virus, including IFI27, IFIT1, IFI6, IFITM3, and GBP3, and both groups induce expression of MHC-I and MHC-II genes (HLA-A, HLA-C, HLA-F, HLA-E, HLA-DRB1, HLA-DRA) and other factors involved in antigen processing and presentation (Figures 3B and S4B). Here, HLA-DRA is linked to COVID-19.