Immunodiagnosis of human malignancy

Abstract

Definition of normal cell membrane antigens using immunologic techniques has permitted investigators to distinguish normal cells from malignant cells. Malignant cells express fetal antigens in concentrations different from normal mature cells. Mutant cells express differentiation as well as those antigens reflecting the altered cell genome. Normal cells can be transformed into malignant cells using either chemical agents or viruses. As these agents are incorporated into the genome, surface antigens are expressed that differ from normal cell isoantigens. These antigenic determinants can serve as tumor-associated or perhaps tumor-specific markers. Immunochemical methods now exist that permit isolation and purification of these antigens. Monoclonal antibodies have been generated that react with single epitopes associated with these antigens. Very sensitive and highly specific radioimmunoassays and enzyme immunosorbent assays can detect microgram quantities of these antigens in body fluids and as such permit serodiagnostic evaluation. Monoclonal antibodies can also be used for radioautography, immunofluorescent, and immunoperoxidase staining for diagnostic purposes of both cytologic and fixed tissue sections. The binding affinity and specificity of these monoclonal antibody reagents has successfully been used for in vivo tumor localization. Isotopically labeled monoclonal antibodies bind preferentially to tumor cells in the host and are useful for specific radionuclide scintigraphy. These recently developed immunodiagnostic techniques not only add specificity in terms of diagnostic accuracy but are useful for early detection of recurrent disease and in vivo localization of tumor deposits. Therapeutic implications are discussed.