Abstract
The enhancing effect of mini-cells of Salmonella typhimurium which do not contain chromosomal DNA on anti-tumor immunity in mice was studied. The growth of sarcoma 180 cells which were subcutaneously transplanted into ICR mice was significantly retarded in mice treated with Salmonella mini-cells at the same time or 7 days after S180 transplantation, while no or only a little growth inhibition was observed in mice treated 7 days prior to S180 transplantation. Treatment with mini-cells inoculation alone did not increase the survival time of mice that had received intraperitoneal transplants of S180 cells. However, a statistically significant increase of survival time was observed in mice treated with a combination of mini-cells and surgical resection of subcutaneous tumors when S180 cells were injected 7 days after the surgical resection. The injection of mini-cells restored macrophage chemotaxis in S180-bearing mice in which macrophage chemotaxis was greatly retarded but lymphocyte activity was not.