Augmentation of the Adoptive Transfer of Specific Tumor Immunity by Nonspecifically Immunized Macrophages2

Abstract

The ability of normal and BCG-immune peritoneal exudate cells to assist tumor-immune lymph node cells in tumor killing was studied. The adoptive transfer of 9 × 10⁶ tumor-immune lymph node cells mixed with 3 × 10⁶ BCG-immune peritoneal exudate cells to normal syngeneic hamsters significantly suppressed the growth of 3 × 10⁶ tumor cells. Neither cell population alone or combined with nonimmunized cells affected tumor growth at these cell concentrations. Thus nonspecifically immunized macrophages could partake in tumor killing in vivo, but to do so they required the assistance of specifically immunized cells, most likely lymphocytes. This form of cooperative Interaction between lymphoid cells and macrophages differed somewhat from previous reports in that the addition of the antigen to which the macrophageswere sensitized was not required for the cooperative event to occur. We suggest that, in the presence of specific tumor antigen, immune lymphocytes can cause macrophages to release their contents that are toxic for some “bystander” cells. However, some tumor cells are resistant to the products released by normal macrophages but may be sensitive to those from nonspecifically immunized or “activated” macrophages.