As reported, in the experimental model of Con A administration, the cytotoxicity effector molecules, and the receptors of them, such as perforin-granzyme, FASL/FAS, TNF-α, and TRAIL/DR5 in the pathway of natural killer cell mediated cytotoxicity play crucial roles for hepatitis development as well as hepatocyte cell death (Gantner et al., 1995; Watanabe et al., 1996; Kunstle et al., 1999; Zheng et al., 2004). The gene discussed is PRF1; the disease is hepatitis A virus infection.