Regarding the downregulated geneset, MHC II molecules, including HLA-DQA1, HLD-DRA, HLA-DRB1, HLA-DMB, HLA-DMA, etc., and cytokine/chemokine genes, including IL1B, TNF, CCL3, CCL4, and CXCL8 were expressed at lower levels in COVID-19 patients, especially those with severe diseases (Fig. 2e). The gene discussed is CCL4; the disease is COVID-19.