Because immunization with Hsp-peptide complexes derived from infected cells is directed against the entire antigenic repertoire, it drastically reduces if not eliminates the possibility of development of escape variants. cancers of a wide variety, including those induced by chemical carcinogens and UV radiation and spontaneous cancers as well. Second, immunity to malignancy was specific for each individual malignancy. Mice were protected from challenge only with the specific malignancy that was used to immunize. Thus, the malignancy antigens were not cancer specific or malignancy type specific (eg, hepatoma specific) but were individually specific. Cross-reactive protection was observed in some studies, but, with notable exceptions (Donawho and Kripke 1990; Frey and Cestari 1995), such immunity was Vorapaxar (SCH 530348) substantially weaker than the individually specific immunity (Coggin and Anderson 1974). The 2 2 tenets led Vorapaxar (SCH 530348) to a search for individually cancer-specific antigens, the philosopher’s stones of malignancy immunology. In early methods, cancers and their normal counterparts were analyzed by high-resolution electrophoretic methods to identify Vorapaxar (SCH 530348) cancer-specific bands or spots. Extensive studies with antibodies, first polyclonal and then monoclonal, scanned the surfaces of human and mouse malignancy cells to determine cancer-specific antigens (Old 1981). Although these studies were immensely productive in definition of the composition of the mammalian cell surface and helped identify a number of important molecules, no truly cancer-specific molecules were recognized and characterized as a result. Identification of cancer-specific molecules recognized by T lymphocytes did not come into vogue until recently (Monach et al 1995; Boon and van der Bruggen 1996), because methods for doing so were previously unavailable. With few exceptions (Coulie et al 1995; Monach et al 1995; Robbins et al 1996; Ikeda et al 1997), these studies too have generally recognized molecules shared between cancers and normal tissues. Another approach to the problem was to look for the cancer-specific antigens by their ability to elicit protective immunity to malignancy difficulties, ie, by the very assay that pointed to their presence. This approach typically involved fractionation of malignancy homogenates into numerous protein components by standard chromatographic methods (observe Srivastava et al 1998 for review). The fractions thus obtained were used to immunize animals, which were then challenged with live malignancy cells. The fractions that elicited protection against the malignancy were then refractionated and the malignancy rejection assay repeated until apparently homogeneous preparations were obtained. This approach, with variations, led to identification of cancer-rejection molecules from cancers of diverse histological origins, induced in mice and rats of different haplotypes by chemicals or UV radiation, or of spontaneous origin. The cancers ranged in immunogenicity from your nonimmunogenic (eg, the Lewis lung carcinoma) to the highly immunogenic regressor cancers induced by UV radiation. Surprisingly, all the well-characterized molecules identified by this method turned out to be heat shock proteins (Hsps) of the Hsp90 or the Hsp70 family, including gp96, calreticulin (Basu and Srivastava 1999), Hsp70, and Hsp90. The first of the 2 2 tenets of malignancy immunity, that cancers elicit protective immunity in syngeneic hosts, experienced thus achieved a molecular definition. Consistent with tenet 2, the Hsps purified from a given cancer were observed to elicit protective immunity specific to that particular cancer. Hsps derived from normal tissues did not elicit protective immunity to any cancers tested (Udono and Srivastava 1994). The observed specificity of immunogenicity of cancer-derived Hsps would suggest Hsps to display somatic polymorphism, such that Hsps would differ between cancers and normal tissues and from one cancer to another. However, considerable sequencing studies of Hsp complementary DNAs of cancers and normal tissues did not support this idea (Srivastava 1993). What is the origin of the specificity TRAIL-R2 of immunogenicity? SEARCH FOR SPECIFICITY: DISCOVERY OF Hsp-ASSOCIATED PEPTIDES Because the Hsp preparations used to immunize were homogeneous by all criteria tested, the possibility was envisaged that low-molecular-weight Vorapaxar (SCH 530348) substances, Vorapaxar (SCH 530348) not detectable by polyacrylamide gel electrophoresis, are associated with Hsps and are responsible for the specificity of immunogenicity of Hsp preparations (Srivastava and Heike 1991; Srivastava and Maki 1991). This idea gained some credence when a seemingly large collection of peptides was shown to be associated with apparently homogeneous gp96 preparations (Li and Srivastava 1993). Formal proof for the idea came when depletion of peptides from tumor-protective Hsp70 preparations rendered them ineffective in immunizing against malignancy cells.