Consistent with the apoptosis trend of Tim-3+ NKT cells, an elevated expression level of almost all caspase genes in Tim-3+ NKT cells was observed in controls and patients with mild and severe COVID-19, especially caspase-2, caspase-3, caspase-6, and caspase-9 (Figure 4F). This evidence concerns the gene CASP9 and COVID-19.