Immune Elimination of Host Fibroblasts for the Cultivation of Human Tumors Transplanted into Nude Mice1

We report here a useful method for the isolation and culti vation of human tumor cells in vitro from human tumors grown in nude mice. A rabbit was immunized with spleen cells ob tained from adult nude mice. The rabbit antiserum in the presence of complement effectively killed cultured cells derived from various mouse tissues, but it was not cytotoxic to cultured cells from human tissues including tumors. When mixed cul tures consisting of human tumor cells and nude mouse fibroblasts were treated with the antiserum and complement, the nude mouse fibroblasts were completely removed from the cultures, and the human tumor cells could be propagated without noticeable changes in morphological features. Primary cultures of heterotransplanted human tumors grown in nude mice were also successfully treated, resulting in the ultimate elimination of fibroblastic cells derived from the stroma of the tumor. The functional properties of the tumor cells (production of human chorionic gonadotropin by choriocarcinoma cells and production of carcinoembryonic antigen by pancreas carcinoma cells) were also maintained after the antiserum treatment.