Oncological consequences of impaired immune surveillance against ubiquitous viruses

The immune system is constantly challenged by ubiquitous viruses. Multiple immune defenses have evolved to meet these challenges, and thus immunocompetent individuals successfully respond to infection without sequela. X-linked lymphoproliferative syndrome patients, renal allograft recipients, and acquired immunodeficiency syndrome patients share impaired immune surveillance as a common feature. Such individuals are variously susceptible to numerous untoward complications following infection with Epstein-Barr virus, cytomegalovirus, herpes simplex virus, human papillomavirus, and hepatitis B virus. We hypothesize that failure of the immune system to control these viruses is instrumental in the occurrence of some B-cell lymphomas. Kaposi's sarcoma, and squamous-cell and hepatocellular carcinomas. Herein we review some mechanisms responsible for the breakdown of immune surveillance and the permissive role immunodeficiency plays in viral oncogenesis.