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Live proliferation-competent and Irradiated proliferation-incompetent L5178 murine lymphoma cells (Eb cell line) were compared for their potency to induce systemic anti-tumor Immunity in syngeneic DBA/Z mice. The tumorigenic potential in vivo of live Eb cells was suppressed through local secretion of interleukin 4 (IIA) Failure to develop effective tumor-rejection immune responses has been suggested to be due to a deficiency of help generated within the immune system (1, 2). In accordance with this postulate, the potential immunotherapeutic effects of a number of lymphokines have been tested through immunization of syngeneic or immunodeficient animals with tumor cell lines that have been engineered to secrete particular lymphokines for help. Protocols using multiple vaccinations at optimal doses have been successful in identifying combinations oftumor systems and lymphokines where local lymphokine secretion is effective for systemic anti-tumor protection (3) or even in the therapy of established micrometastases (4). Other recent investigations (using singlevaccination protocols) have found that, with the exception of granulocyte/macrophage-colony-stimulating factor, local secretion of lymphokines achieve little if any improvement on the immunogenicity of the irradiated parental tumor cells (5,6).The present investigation addresses the influence of tumor cell viability (when used as vaccine) on the induction and maintenance oflong-lasting anti-tumor immunity. To this aim we have employed the well-characterized L5178 lymphoma line Eb, which expresses characteristic Kd-associated tumor antigens and elicits specific cytotoxic T-cell responses in immunized or tumor-bearing syngeneic hosts (7-9). Vaccination of syngeneic DBA/2 mice with live tumor cells was achieved either through local secretion of interleukin 4 (1L4), which is known to render tumor cells nontumorigenic (10,11) 7430The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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