title: Rapid detection of macroprolactin in the form of prolactin-immunoglobulin G complexes by immunoprecipitation with anti-human IgG-agarose.
abstract: Immunoprecipitation with anti-human immunoglobulin G-agarose was evaluated for the detection of prolactin-immunoglobulin G (PRL-IgG) complexes in macroprolactinemic samples from hyperprolactinemic patients (prolactin measured using the automated Elecsys PRL assay; Roche Diagnostics, Mannheim, Germany). Using the polyethylene glycol (PEG) precipitation test on serum samples with PRL above 1000 mIU/l, we detected macroprolactin in 38 out of 175 samples with a recovery below 50%. Gel filtration chromatography on a subset of hyperprolactinemic samples confirmed that macroprolactin was the predominant immunoreactive form of PRL in samples which showed a recovery < or = 50%. In 37 out of 38 samples containing macroprolactin, immunoprecipitation with anti-human IgG (anti-hIgG)-agarose revealed a higher PRL-binding (19.1-91.3%) than in the sera containing monomeric PRL (< 10%). In conclusion, we found that PEG precipitation detected macroprolactin in 21.7% of samples with elevated PRL levels as measured by the Elecsys PRL assay, and that in the vast majority of these samples the presence of PRL-IgG complexes could be demonstrated by immunoprecipitation with anti-hIgG-agarose. In view of the high prevalence of PRL-IgG complexes in hyperprolactinemic patients and the simplicity of the test, immunoprecipitation with anti-hIgG-agarose might play a role in the routine laboratory handling of hyperprolactinemic samples, especially with regards to PRL assays where PEG causes interference.
authors.affiliation: Laboratory of Radioimmunology, University Hospital, Brussels Free University (Dutch speaking), Belgium. Johan.Schiettecatte@az.vub.ac.be
authors.forename: J
authors.initials: J
authors.lastname: Schiettecatte
authors.forename: J
authors.initials: J
authors.lastname: De Schepper
authors.forename: B
authors.initials: B
authors.lastname: Velkeniers
authors.forename: J
authors.initials: J
authors.lastname: Smitz
authors.forename: A
authors.initials: A
authors.lastname: Van Steirteghem
mesh_terms: D000936:Antigen-Antibody Complex / Q000097:blood* / Q000276:immunology; D006801:Humans; D006966:Hyperprolactinemia / Q000097:blood* / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D011092:Polyethylene Glycols; D011233:Precipitin Tests; D011388:Prolactin / Q000097:blood*; D015203:Reproducibility of Results; D012685:Sepharose
chemical_list: D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D011092:Polyethylene Glycols; D011388:Prolactin; D012685:Sepharose