CD8A and COVID-19: Multiple studies have associated alterations in blood cell proportions with COVID-19 severity, including enrichment of neutrophil precursors, MDSCs, HLA-DRlo monocytes and CD169+ activated monocytes, depletion of HLA-DRhiCD11chi inflammatory monocytes and CD4+, CD8+ and γδ T cells, T-cell exhaustion and an increased ratio of CD8+ effector T cells to effector memory T cells8,13,18–24.