CD4 and infectious mononucleosis: As a result of complete or unsuccessful viral replication, immunodeficiency viruses may functionally lyse or impair immune cells such as lymphocytes, as observed in parvovirus infections of B lymphocytes, in infectious mononucleosis due to Epstein–Barr virus, and in CD4+ T lymphocytes and macrophages in AIDs caused by HIV lentivirus (58, 59).