Progress and obstacles in the development of an AIDS vaccineNorman L. Letvin(Beth Israel Deaconess Medical Center)Nature reviews. ImmunologyNovember 24, 200610.1038/nri1959Cited by 173SaveCiteExport RISWatch citationsRelated PapersIL-21 Induces Apoptosis of Antigen-Specific CD8+ T Lymphocytes|The Journal of Immunology|2007|33