Thus, EBNA-1-specific cytotoxic CD4 T lymphocytes appear to have a protective role in vivo, as deduced from their reduction/absence or altered function in the EBV-associated diseases discussed here, and in other diseases, such as post-transplant lymphoproliferative disease (PTLD) [269] and in EBV-related Hodgkin’s and non-Hodgkin’s lymphomas [15,75,270,271,272,273]. The gene discussed is CD4; the disease is post-transplant lymphoproliferative disease.