ABSTRACT
This chapter discusses the considerable progress toward this goal has been made using the techniques of molecular biology to alter immunological responses to tumor cells. A balance between cell division and programmed cell death or apoptosis is essential to maintain stability within multicellular organisms. The immune system is only one of the factors determining if a tumor will progress or regress. Cell-mediated immune responses are an important part of the defense against cells expressing foreign antigens on their surfaces after infection with intracellular pathogens such as viruses, protozoa, and certain bacteria. Immunization against tumors has been a popular idea since the end of the nineteenth and extending well into the twentieth century. The belief was held that if one could immunize an individual against pathogens foreign to the host, it must also be possible to immunize against a tumor, which is also foreign to the host.
