ABSTRACT
Human papilloma viruses (HPV) are familiar to all gynecologists, as some types (6, 11 and their relatives) are predominantly associated with benign anogenital warts or condylomata, while other types (the high-risk types-16, 18, 31, 33, 35, 45) are associated with anogenital cancers and intraepithelial lesions, particularly of the cervix. HPV are ubiquitous, and population-based serological studies show that most people who have been sexually active have antibodies to HPV, indicating that their immune system has encountered HPV at some point. Yet cervical cancer is relatively uncommon-there are only approximately 4000 new cases of invasive disease in the UK annually. It has tempted some to suppose that those women who develop precancer or cancer of the cervix are the ones who have encountered the high-risk types, while the rest have come across only low-risk HPV, This is, however, unlikely to explain the full picture. The general assumption is that there is some ill-defined immunological defect (perhaps at the local level, rather than a generalized defect) in those women who develop cancer, but the defect has yet to be defined. The notion of an ‘immunosurveillance system’ against cancer is widely believed, but whether it exists, and its nature, are subjects of debate and speculation. The link with the concepts regarding survival of the fetal allograft are clear enough: a cancer cell has undergone a transformation such that it should no longer be regarded as ‘self’, and presumably this is why cancer does not occur more frequently; the immunosurveillance system detects the ‘non-self’ cancer cells and destroys them, but as with any system, either the cancer cells develop ways of circumventing the ‘immunological guards’, or the latter become less efficient, or less energetic, allowing cancers to develop-which might explain why cancers are more common with increasing age! Many will have heard of cancer-related genes, and the gene p53 is known by many without an appreciation of what it is and its role in cancer. This chapter explores cancer and the immune system, with particular emphasis on gynecological malignancy.
