Strikingly, we observed that more than 95% of animals with CD8+ T-cell frequencies exceeding a threshold of 1% of total PBLs were protected against sporozoite challenge, while more than 95% of animals with CD8 T-cell frequencies below this threshold developed blood-stage infection and were thus not sterilely protected (Schmidt et al., 2008). The gene discussed is CD8A; the disease is infection.