Presence of immunoglobulin G in human sera binding to alphafetoprotein.
Sera from patients with collagen diseases, chronic liver diseases and hepatocellular carcinoma were analysed for alphafetoprotein (AFP)-binding protein. The method used was a 125I-labeled AFP-binding assay with goat anti-human immunoglobulin G (IgG) as the precipitating antibody. AFP-binding IgG was found in the sera from one of 34 patients with systemic lupus erythematosus (SLE) and one of nine patients with hepatocellular carcinoma. This protein may interfere with the conventional radioimmunoassay of human AFP, and may be of interest because of its usefulness as a carrier of radioactivity or therapeutic agents to AFP-producing tumors.