Abstract
The development and growth of transplanted syngeneic Lewis lung carcinoma and their relation to aging was investigated. The Lewis lung carcinoma (3LL) is a metastasizing tumor which developed spontaneously in a C57BL/6J mouse. We found that the frequency and rate of tumor growth were increased when the tumors were implanted in aged as compared to young mice. In order to determine whether this finding involves the participation of the immunological system of the host, spleen cells of mice at various ages were mixed with tumor cells at a ratio of 100:1 and injected into one footpad of syngeneic recipient mice. Spleen cells from older mice were found to strikingly enhance tumor growth in the recipient. Only living T cells were responsible for this enhancement, since in vitro irradiation of donor spleen cells or use of spleen cells from thymectomized donors abolished this enhancement. The quantitative distribution of various cell populations in the spleen did not vary greatly with age, these results suggesting that a change occurs in the intrinsic properties of lymphoid cells during aging. It is suggested that the tumorβenhancing properties of aged lymphoid cells are due to autoimmune activity of the cells. Indeed, cellular autoimmune activity was detected when these cells were injected into adequate animals.
Various other features of cellβmediated immunity were analyzed in groups of young and old mice.