Although CD8+ T cells are recognized as vital factors in the control of EBV infection, NK cells are increasingly being acknowledged as important during infectious mononucleosis, as evidenced by the severe EBV-related outcomes that occur in several immunodeficiencies involving T and NK cells and/or their cytolysis pathways.45, 46 Other data also support a role for NK cells during infectious mononucleosis, such as the observation that NK cells in vitro preferentially kill EBV-infected cells when the virus transitions into the lytic phase.47 The gene discussed is CD8A; the disease is infectious mononucleosis.