Purification of antithyroglobulin autoantibodies (Ab-Tg) for application in immunodetection- and immunotherapy of thyroid cancer.

Immunotherapy for cancer has been proposed for many years. After several clinical trials only recently some encouraging results have been achieved in immunotherapy of hematologic neoplasm and in immunodetection of solid tumours like ovary and colorectal carcinoma. One of the current problems that limit clinical application is immunogenicity of murine antibodies, on the other hand techniques to obtain human antibodies in large quantities by hybridoma encountered difficulties that delayed their clinical testing. Autoantibodies extracted from human serum might reveal suitable for immuno-detection- and immunotherapy purposes. In order to set optimal conditions Ab-Tg have been purified by immunoadsorbent (CNBr- activated - thyroglobulin- conjugated Sepharose 4B) from a rabbit anti-human thyroglobulin serum and dissociated by acid (ph 3.1) or alkaline (ph 10.5) or SDS (0.3-0.7%). An IgG fraction further purified on a Protein G column was obtained which retains its anti-thyroglobulin activity by haemagglutination, ELISA and RIA. By agarose gel electrophoresis and silver stain this fraction has the mobility of rabbit IgG. Human sera with Ab-Tg were similarly processed obtaining an IgG fraction which retains its binding to thyroglobulin (ELISA) and has the same electrophoretic mobility as human IgG. In conclusion we have purified human Ab-Tg not denatured and in concentration suitable to the targeting of thyroglobulin expressed at the microvilli bearing surface of tumor cells in differentiated thyroid carcinoma.