Role of immune mechanisms in metastatic patterns of hemopoietic tumors in rats.

Two hemopoietic tumors induced in rats by Gross leukemia virus and dimethylbenz(a)anthracene, respectively, display distinctive and consistent patterns of metastases, the former in the thymus and lymph nodes, the latter in the liver and spleen. To investigate the role of circulatory anatomy in the localization of metastases, 51Cr-labeled cells were injected i.v., and their distribution was followed at various intervals. To explore the influence of immune mechanisms, Gross leukemia virus- and dimethylbenza(a)anthracene-induced leukemic cells as well as a line of antigenically modulated cells were administered to newborn, X-irradiated, and immunologically unresponsive recipients. The circulation of tumor cells through various organs was indiscriminate. The immune response of the host was operative in limiting the local and metastatic tumor growth but not in determining the site of secondary tumors. The conclusion of these experiments was that the selective organ distribution of tumor metastases was solely dependent on intrinsic cellular properties.