Localization of biotinylated monoclonal antibody in nude mice bearing subcutaneous and intraperitoneal human tumour xenografts

To demonstrate the precise distribution and binding of in vivo injected monoclonal antibodies on histological tumour sections, we have biotinylated our primary antibody AUAI. Biotinylated antibody was injected into nude mice bearing simultaneous subcutaneous and intraperitoncal xenografts of the human tumour LoVo. Twenty‐four hours after injection, the animals were killed, tumours and control organs were removed. Antibody was demonstrated on frozen sections by incubating sections with avidin biotin peroxidase complex. We compared the in vivo penetration and binding of this antibody on intraperitoneal and subcutaneous xenografts. The antibody penetration was mainly restricted to a thin layer of tumour cells adjacent to the vascularized stroma in large solid subcutaneous and intraperitoneal tumours, whereas in very small intraperitoneal tumours, antibody penetration was complete. These findings were similar to our autoradiographic results. This study demonstrates that employing the biotinylated antibodies for in vivo localization studies provides superior resolution of antibody binding for morphological assessment compared to autoradiography. Localization of a biotin label is more precise and will permit ultra‐structural studies.