Since the bradyzoites maintain expressions of GRA and ROP proteins (9, 10), and since some of GRA and ROP proteins have been shown to disrupt the effector mechanisms of IFN-γ-mediated protective immunity against tachyzoites (11–13), it would be possible that certain GRA and/or ROP proteins mediate the evasion of T. gondii cysts from the perforin-mediated anti-cyst CD8+ T-cell immunity. The gene discussed is PRF1; the disease is cyst.