The role of immune factors in the survival of circulating tumor cells.

The effects of immune serum on the survival of hematogenously disseminated malignant cells were investigated in six murine tumor systems with varying immunogenicity. Blood containing circulating tumor cells demonstrable by bioassay was obtained from donor mice with disseminated tumor. The cellular fraction was isolated by centrifugation and resuspended in immune serum obtained from donor animals bearing the same tumor (Group 1), in immune serum from mice bearing a differing tumor (Group 2), or in normal nonimmune serum (Group 3). The mixed cellular and serum fractions were intravenously inoculated into normal recipient mice which were subsequently scored for the development of pulmonary tumors. Similar incidence (35-50%) of pulmonary tumor deposits were seen in Groups 2 and 3. A significant enhancement in the incidence of lung tumors was present in the Group 1 animals for all tumor systems studies. It was suggested that the observed enhancement resulted from factors present in isologous immune serum but absent from both normal serum and immune serum obtained from hosts bearing heterologous tumors.