The immune system during the precancer period: naturally-occurring tumor reactive monoclonal antibodies and urethane carcinogenesis.

Previous results obtained in our laboratory suggested that natural antibodies reactive with L5178Y lymphoma cells play a role in the induction of lung tumors by the chemical carcinogen urethane. In order to characterize some of the naturally-occurring L5178Y reactive antibodies we prepared hybridomas that secreted natural monoclonal IgM antibodies reactive with L5178Y lymphoma cells. In the present study we characterized some of these antibodies and provided further proof as to their role in urethane carcinogenesis.

B16 melanoma development, NK activity cytostasis and natural antibodies in 3 and 12 month old mice.

Three types of natural immune responses against malignant cells were studied in vitro: Cytotoxicity mediated by splenic NK cells; cytostasis mediated by splenocytes and binding of naturally occurring antibodies to various tumour targets. These responses were studied in untreated 3 and 12 month old mice and in mice of both age groups inoculated with B16 melanoma cells. The results showed that in normal mice NK activity decreases with age, cytostatic activity remains unchanged and the titre of natural antibodies increases.

Studies on the level of natural antibodies reactive with various tumor cells during urethane carcinogenesis in BALB/c mice.

Serum from young normal BALB/c mice was found to contain IgM antibodies able to mediate complement-dependent lysis of certain syngeneic or allogeneic tumor target cells. The titer of such naturally occurring antitumor antibodies ( NATA ) was found to increase with aging. A longitudinal serological study comparing the cytotoxicity potential of NATA from normal and from urethan-treated BALB/c mice was performed.

Lymphocytotoxic autoantibodies eluted from in vivo propagating sarcoma cells of mice.

Eluates of SEYF-a cells (from polyoma virus-induced sarcoma grown in A.BY mice) containing cytotoxic anti-SEYF-a antibodies mediated complement-dependent cytotoxicity of normal lymph node cells. Some lymphocytotoxicity was also mediated by sera of tumor-bearing mice, but the pattern of cytotoxicity was different from that exhibited by tumor eluates.