title: Detection of peanut allergen in human blood after consumption of peanuts is skewed by endogenous immunoglobulins.
abstract: Some studies have suggested that allergens may appear in the circulation after ingestion of allergenic food sources. The reported levels of allergen in serum, however, are low, and conclusions between studies differ. Here, we investigated factors that determine the detection of allergens in serum after consumption of peanuts. Ten healthy volunteers ingested 100g of light-roasted peanuts. Serum samples were taken at regular intervals for six hours. A double monoclonal sandwich ELISA was used to analyse the presence and quantity of the major peanut allergen Ara h 6 in serum. In 4 out of 10 subjects, no Ara h 6 could be detected. Purified Ara h 6 that was digested in vitro was still reactive in the ELISA, rejecting the possibility that digestion leads to small peptides that could not be detected. Spiking of purified Ara h 6 in baseline serum showed that the pre-ingestion serum of these four subjects partially prevented Ara h 6 to react in the ELISA, with a reduction of reactivity of up to 3 orders of magnitude or more. Pre-ingestion serum of the other six subjects did not show such an effect. The reduction of reactivity of Ara h 6 coincided with high titres of IgG and IgG4, and removal of IgG from pre-ingestion serum abolished this effect completely, indicating that IgG and IgG4 inhibited the reactivity of Ara h6 in the ELISA. We conclude that some individuals have IgG and IgG4 against food allergens in their blood, which interferes with detection of such food allergens in serum. Because this effect does not occur for each individual, the possibility of such interference should be taken into consideration when interpreting immunochemical studies on the absorption of food allergens in serum.
authors.affiliation: Wageningen Food and Biobased Research, Wageningen University and Research, The Netherlands; Nutrition and Pharmacology, Wageningen University and Reserach, The Netherlands; Human and Animal Physiology, Wageningen University and Research, The Netherlands.
authors.forename: Lonneke M
authors.initials: LM
authors.lastname: JanssenDuijghuijsen
authors.affiliation: Wageningen Food and Biobased Research, Wageningen University and Research, The Netherlands.
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Wichers
authors.affiliation: Nutrition and Pharmacology, Wageningen University and Reserach, The Netherlands.
authors.forename: Klaske
authors.initials: K
authors.lastname: van Norren
authors.affiliation: Human and Animal Physiology, Wageningen University and Research, The Netherlands.
authors.forename: Jaap
authors.initials: J
authors.lastname: Keijer
authors.affiliation: Food Allergy Research and Resource Program, Food Science and Technology, University of Nebraska, Lincoln, United States.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Baumert
authors.affiliation: TNO, Zeist, The Netherlands.
authors.forename: Govardus A H
authors.initials: GA
authors.lastname: de Jong
authors.affiliation: Nutrition and Pharmacology, Wageningen University and Reserach, The Netherlands.
authors.forename: Renger F
authors.initials: RF
authors.lastname: Witkamp
authors.affiliation: Food Allergy Research and Resource Program, Food Science and Technology, University of Nebraska, Lincoln, United States. Electronic address: stefkoppelman@zonnet.nl.
authors.forename: Stef J
authors.initials: SJ
authors.lastname: Koppelman
mesh_terms: D055516:2S Albumins, Plant / Q000097:blood* / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology; D052179:Antigens, Plant / Q000097:blood* / Q000276:immunology; D010367:Arachis / Q000009:adverse effects / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D004063:Digestion; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D000939:Epitopes; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D006868:Hydrolysis; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D021183:Peanut Hypersensitivity / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult
chemical_list: D055516:2S Albumins, Plant; D000911:Antibodies, Monoclonal; D052179:Antigens, Plant; C492737:Ara h 6 allergen, Arachis hypogaea; D015415:Biomarkers; D000939:Epitopes; D007074:Immunoglobulin G
keywords: Ara h 6; ELISA; immunoglobulin G; inhibition; peanut allergen