Furthermore, we observed that SARS-CoV-2 infected patients had lower expression of genes involved in NK cell cytotoxicity such as perforin (PRF1), granulysin B (GNLY) and CD107a (LAMP1), an observation which is consistent with studies analyzing intracellular expression patterns of NK cells from COVID-19 patients (59, 62). This evidence concerns the gene PRF1 and COVID-19.