GZMK and COVID-19: We found a significantly increased expression (% and/or MFI) of perforin (PRF), granzyme A (GZMA), granzyme B (GZMB), and granzyme K (GZMK) in NK cells of COVID-19 WARD patients, whereas these were not different in ICU patients compared to HCs, except for GZMA that was decreased and GWMK that was increased (Figure 3A upper panels).