Plasma leakage grade, endothelial dysfunction (angiopoietin-2, sydnecan-1, VCAM-1) and the severity-related biomarker (ferritin) positively correlate with expression of NK-cell inhibitory markers (LILRB1, NKG2A, PD-L1) and negatively correlate with the frequencies of activated and cytotoxic NK-cells (CD69+, NKG2D+, GzmB+ perforin+; Fig. 6e). Here, PRF1 is linked to endothelial dysfunction.