HLA-DRB5 and COVID-19: Of note, COVID-19 (high-viral-load samples), influenza, and ARDS each show differential HLA-B and -C expressions, which are known mediators of NK and T cell activation21,22 and which can mediate host risk of infection; one example is enrichment for HLA-DRB5, whose expression and specific gene polymorphisms are associated with pulmonary fibrosis and severity.23