Clin Chem. 1988 Jun;34(6):1071-6.

Confirmation of a false-positive result in CA 125 immunoradiometric assay caused by human anti-idiotypic immunoglobulin.

Clinical chemistry

T L Klug, P J Green, V R Zurawski, H M Davis

PMID: 2454168

Abstract

An immunoradiometric assay (IRMA) involving a monoclonal antibody (MAb OC125) to an ovarian carcinoma-associated antigenic determinant (CA 125) has been tested as one component in a strategy for early detection of epithelial ovarian cancer. We characterized one confirmed "false-positive" sample by murine antibody blocking studies, Western blotting, immunoaffinity, size-exclusion chromatography, and reactivity with polyclonal rabbit antisera to CA 125 antigen. The positive response of this serum in the CA 125 IRMA was due to a human IgM. The discrepant IgM was isolated from the serum by successive immunoaffinity steps with nonspecific murine MAb, MAb OC125, and goat antibodies to human IgM Fc. Purified IgM inhibited the binding of MAb OC125 to CA 125. Furthermore, rabbit antisera to CA 125 antigen competitively inhibited the binding of MAb OC125 to both CA 125 and the discrepant IgM. The discrepant activity thus appears to reflect binding of this human IgM to a idiotope of MAb OC125. Radioiodination of MAb OC125 by a different technique eliminated the discrepant activity and decreased the incidence of CA 125 positivity in an at-risk population of apparently healthy women, increasing the specificity of the IRMA to 99.8% in this group.

Substances

• Antibodies, Anti-Idiotypic
• Antibodies, Monoclonal
• Antigens, Neoplasm
• Antigens, Surface
• Antigens, Tumor-Associated, Carbohydrate
• Epitopes
• Immunoglobulin Fab Fragments
• Immunoglobulin G
• Immunoglobulin Idiotypes
• Immunoglobulin M
• Iodine Radioisotopes

MeSH terms

• Adult
• Animals
• Antibodies, Anti-Idiotypic / immunology
• Antibodies, Monoclonal / immunology
• Antigens, Neoplasm / analysis
• Antigens, Neoplasm / immunology
• Antigens, Surface
• Antigens, Tumor-Associated, Carbohydrate
• Chromatography, High Pressure Liquid
• Epitopes
• False Positive Reactions
• Female
• Humans
• Immunoassay*
• Immunoglobulin Fab Fragments
• Immunoglobulin G
• Immunoglobulin Idiotypes / immunology
• Immunoglobulin M / immunology
• Immunoglobulin M / isolation & purification
• Iodine Radioisotopes
• Isotope Labeling
• Mice
• Ovarian Neoplasms / immunology

Publication Types

• Case Reports
• Journal Article
• Research Support, U.S. Gov't, P.H.S.

Grant support

• R433 CA 40945-01/CA/NCI NIH HHS/United States

LinkOut - more resources

• Research Materials
  • NCI CPTC Antibody Characterization Program
• Other Literature Sources
  • The Lens - Patent Citations