While the immunological mechanisms underlying the high grade protection induced by these whole parasite vaccines remain unclear, animal studies demonstrate dependence on cell-mediated immunity (CMI), in particular cytotoxic CD8+ T cells [6], [7] which release cytotoxins to lyse the malaria-infected hepatocyte or interferon gamma (IFN-γ) to trigger nitric oxide production [8], [9]. The gene discussed is CD8A; the disease is malaria.