Moshe Glaser

IMMUNOGENICITY OF TUMOR ANTIGENS

A central theme in experimental tumor immunology is the immunization with tumor antigens. The objectives of the studies on this subject have usually been the induction of either transplantation protection against tumor challenge or of in vitro immune reactivity. Few detailed studies have been performed to determine mechanisms for in vivo immunogenicity, by relating those data to results obtained in vitro. In this paper, we will describe a series of experiments performed primarily with virus-induced tumors of mice and rats, in which some of the factors that may influence in vivo immunogenicity are analyzed. It has become clear from these studies that some “nonimmunogenic” tumors or tumor cell preparations are antigenic and under some circumstances can induce an immune response in the host. We have placed particular emphasis on lymphoproliferative responses and on cell-mediated cytotoxic reactions, after primary or secondary exposure to tumor antigens in vivo or in vitro, and these experiments have been quite helpful for the analysis of immunogenicity. A number of factors have been identified that may interfere with immunogenicity of antigenic tumors: Suppressor cells in the host, immunosuppressive viruses in the tumors, and specific and nonspecific serum factors. Careful dissection of factors influencing immunogenicity of tumor antigens should help to provide practical solutions to problems related to immunoprevention and immunotherapy of cancer, which have not been solved by empirical studies.

Inhibitory effect of alpha-globulin on the second set allograft reaction.

Summary α-Globulin fraction prepared from normal human plasma suppressed first as well as second set skin allograft reactions in rats. Spleen cells taken from mice, immunized by transplantation of skin allografts, and incubated with the α-globulin fraction failed to transfer transplantation immunity to isologous recipients. No evidence was obtained for cytotoxicity of α-globulin. Since human serum albumin failed to suppress immune response the mode of action of α-globulin was not considered to be due to antigenic competition.