KLRK1 and systemic lupus erythematosus: IL-15 enhanced the NKG2D expression of NK cell in SLE patients (1921.9±178.9 MFI vs. 1361.8±98.1 MFI, p<0.001), but not controls (2317.1±305.4 MFI vs. 2192.0±180.5 MFI, p = 0.959).