[The biological behaviors of inoculated B16 melanoma in mice: correlation with NK activity of the host].

B16 melanoma cells with different natural killer (NK) cell activity were inoculated subcutaneously in mice. Observations were made on the relation of NK cell activity to tumor growth, infiltration and metastasis on the one hand and, the sensitivity of the tumor cells to NK cells before and after tumor implantation on the other. It was seen that NK cells could not only inhibit tumor growth, infiltration and metastasis, but also induce tumor NK-tolerance of the tumor. When the NK-tolerant tumors were resected and implanted into ordinary mice, the biological behaviors of NK-tolerant B16 tumor cells were more malignant than wild (original) B16 cells. The results of this study show that the in vivo interaction between NK cells and tumor cells can positively and negatively influence the tumor's biological behaviors.