Considering the correlation of IL-15 levels and NKG2D expression, we then examined the CD122 (IL-15Rβ) +NKG2D+ phenotypes in EBV and CMV-derived bystander memory CD8+ T cells in PBMC (Peripheral blood mononuclear cell) of HFRS patients (Figure 4A). Here, IL15 is linked to hemorrhagic fever with renal syndrome.