Comparison between the disease conditions indicated significantly stronger expression of certain NK cell receptors (CD160, KLRC2, KLRC3, KLRF1, KIR3DL2, NCR1, NCR3) along the SLEC lineage in mild COVID-19 compared to severe COVID-19 (Figures 3D, S4C, D). This evidence concerns the gene KLRC3 and COVID-19.