PRF1 and hemorrhagic fever with renal syndrome: Although no significant differences were observed between HFRS patients and uninfected controls in the frequencies of perforin+ or granzyme B+CD56dimNKG2A+ NK cells (Fig 7A-D and 7G-J), the expression of CD107a was significantly higher in mild/moderate and severe/critical HFRS patients compared to uninfected controls (p<0.05 and p<0.01, respectively) (Fig 7E and 7F).