MCEMP1 and COVID-19: Besides demonstrating that the early upregulation of MCEMP1 and downregulation of HLA-DRA expression occurred at least 4 days before the nadir of respiratory function in severe COVID-19 patients [17], emerging studies have also shown an increased accumulation of cells sharing features of M- [46] and PMN-MDSCs [48,50,51,52,53] in severe COVID-19 patients, suggesting the importance of these dysregulated myeloid cells in SARS-CoV-2 pathogenesis and disease progression [52].