The broad objective of the proposed research is to obtain information regarding the role of immunity in the metastatic process and more particularly as it is influenced by removal of the primary tumor. This series of experiments is aimed at determining (1) whether and what host immune factors influence the lodgment of blood borne tumor cells or their destruction in the circulation and how such factors are influenced by the presence or absence of a primary tumor; (2) whether and how the duration of survival of tumor cells following their lodgment is influenced by the presence or absence of a primary tumor; (3) whether and how the host cellular immune response to a metastatic focus is influenced by the presence or absence of a primary tumor; and (4) how the growth and removal of a primary tumor affects macrophage production. Both spontaneous C3H mammary tumors and the more immunogenic methylcholanthrene induced tumors in C3H mice will be employed. Lodgment and retention of tumor cells will be ascertained utilizing labeled tumor cells, neuraminidase treated and untreated. Labeled lymphocytes and macrophages will be employed to gain insight into the temporal sequence of the congregation of such cells at the site of metastatic foci. Studies based on preliminary findings carried out in this laboratory relative to macrophage production in tumor-bearing animals will be performed to gain insight into the role of those cells in tumor destruction. Hopefully, additional information concerning the relationship of a primary tumor and the tumor specific immune response of a host will lead to the formulation of a more rational biological basis for cancer surgery than at present exists.