PRF1 and type 1 diabetes mellitus: The cytotoxic lymphocyte gene products granzyme B (GB), perforin, and fas ligand (FasL) have been shown to play a vital part in the T1D development (Kreuwel et al., 1999; Moriwaki et al., 1999; Kreuwel and Sherman, 2001; Yoon and Jun, 2001).