T h e specificity of a tumor antigen of an experimental ovarian carcinoma was determined by immunofluorescence, cytotoxicity, and immunoelectrophoresis using a n absorbed heterologous tumor antiserum. Tumor controls and normal rabbit sera controls were compared to tumor antiserum-treated recipients. Tumor control animals died by the 36th day after tumor transplantation. Normal rabbit serum was shown to contain a natural antibody which prolonged survival. Treatment with unabsorbed tumor antiserum in vitro led to 100% survival; 24 hours after tumor transplantation 3040% survival; 48 hours after tumor transplantation 50%; and when animals with advanced disease were treated from the 4th-8th day with daily injections this resulted in 30% long-term survivors. T h e intraperitoneal administration of tumor antiserum allows for direct binding with tumor cells without dilution in the circulation and at a reduced risk of nonspecific binding in critical organs and demonstrates the efficacy of serologic immunotherapy.
N EXPERIMENTAL MURINE OVARIAN CAR-
A cinoma has features similar to clinical disease including ascites formation, peritoneal dissemination, and a tumor associated antigen.SJ6.1' The identification of a tumor-associated antigen by the use of a heterologous antiserum led to therapeutic trials with the unabsorbed tumor antiserum. The intraperitoneal administration of the tumor antiserum had the advantage of allowing direct contact of antibody with tumor cells and peritoneal cells prior to possible interaction with normal tissues. The purpose of this study was to evaluate the efficacy and specificity of the tumor antiserum in the immunotherapeutic