Previous studies have shown that gene‐corrected CD8 T cells from Perforin‐deficient or MUNC13‐4‐deficient mice protected mice prophylactically from LCMV‐triggered HLH (Carmo et al, 2015; Tiwari et al, 2016; Soheili et al, 2017; Ghosh et al, 2018; Takushi et al, 2020). Here, PRF1 is linked to hemophagocytic syndrome.