Immunologic Control of the Ascites Form of Murine Adenocarcinoma 755. I. Protection With Syngeneic Immune Serum or Lymphoid Cells 2

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Abstract
The ascites form of the mouse mammary adenocarcinoma 755 (AD755a) that originally arose in a C57BL mouse was used as a model system for the study of the induction of specific tumor immunity. Syngeneic C57BL/6J mice could be immunized against ip challenge with greater than 104 times the dose of AD755a cells necessary to kill 100% of mice by sc inoculation of the cells. The mice were resistant to further challenges for at least 3 months after immunization. Mice hyperimmunized by repeated sc and ip injections of AD755a cells served as donors of immune serum and lymphoid cells, each of which could transfer specific tumor immunity to nonimmunized mice. Protection with immune serum could be transferred with minute quantities of serum (as little as 5 μl) and appeared to have mouse strain specificity. Furthermore, protection against two other mouse tumors, both of which also arose as mammary carcinomas (Ehrlich ascites carcinoma and sarcoma 180), could be achieved by this procedure. Although transfer of protection could be obtained with immune splenocytes and mesenteric lymph node lymphocytes, it could not be obtained with thymocytes. Preliminary results suggested that the protective factor in immune serum was contained in the IgG fraction and had an effective half-life in vivo of greater than or equal to 4.5 days. Initial in vitro and in vivo experiments also indicated that the immune serum led to rosette formation between normal mouse lymphoid cells and the AD755a tumor cells, and these observations were discussed in terms of the possible mechanism(s) of serum-transferred protection.