Studies with animal tumors and clinical evidence are reviewed suggesting that there is difficulty in localization of the usually weak immune response at the site of tumor growth. Concomitant immunity manifesting itself against challenge but not the primary inoculum, and results of immunization with tumor vaccine in the presence of large amounts of tumor in the host may be explained in this manner. Tissue injury apparently aids localization. With various types of inflammation, adjuvants are probably released locally in the host leading to recognition of and response to foreign material which is present. It is suggested that isolation of such adjuvants from the inflammatory process may provide means of augmenting the weak antigenicity seen with syngeneic or autochthonous tumors.
