PRF1 and systemic lupus erythematosus: In patients with systemic lupus erythematosus (SLE) and B6.MRL/lpr mice, NKG2D+ CD4+ T cells that express granzyme B (GZMB) and PRF1 can kill regulatory T (Treg) cells in a manner that depends on NKG2D engagement by NKG2D ligand on Treg cells as well as a partial dependence on Fas-Fas ligand engagement (Yang et al., 2017).