HLA-DRA and COVID-19: Further, we investigated the expression of MHC class II molecules (MHCII) and Fc receptors (FcRs) and found that they were broadly upregulated in APCs in lungs of mild COVID-19 patients, with a MHCII subset (HLA-DRA, HLA-DMB, HLA-DRB1, HLA-DPB1, HLA-DQB1, HLA-DMA) were downregulated (Figure 5B).