title: The challenge of measuring IL-33 in serum using commercial ELISA: lessons from asthma.
abstract: Interleukin-33 (IL-33) has been subject of extensive study in the context of inflammatory disorders, particularly in asthma. Many human biological samples, including serum, have been used to determine the protein levels of IL-33, aiming to investigate its involvement in asthma. Reliable methods are required to study the association of IL-33 with disease, especially considering the complex nature of serum samples.
  
  
  
  We evaluated four IL-33 ELISA kits, aiming to determine a robust and reproducible approach to quantifying IL-33 in human serum from asthma patients.
  
  
  
  IL-33 levels were investigated in serum of well-defined asthma patients by the Quantikine, DuoSet (both R&D systems), ADI-900-201 (Enzo Life Sciences), and SKR038 (GenWay Biotech Inc San Diego USA) immunoassays, as well as spiking experiments were performed using recombinant IL-33 and its soluble receptor IL-1RL1-a.
  
  
  
  We show that 1) IL-33 is difficult to detect by ELISA in human serum, due to lack of sensitivity and specificity of currently available assays; 2) human serum interferes with IL-33 quantification, in part through IL-1RL1-a; and 3) using non-serum certified kits may lead to spurious findings.
  
  
  
  If IL-33 is to be studied in the serum of asthma patients and other diseases, a more sensitive and specific assay method is required, which will be vital for further understanding and targeting of the IL-33/IL-1RL1 axis in human disease.
authors: Division of Respiratory Medicine, University of Nottingham, Nottingham, UK.|University Medical Center Groningen, Department of Pathology and Medical Biology, Laboratory of Allergology and Pulmonary Diseases, University of Groningen, Groningen, The Netherlands.|University Medical Center Groningen, Pediatric Pulmonology and Pediatric Allergology, Beatrix Children's Hospital, Groningen Research Institute for Asthma and COPD, University of Groningen, Groningen, The Netherlands.
authors: M E
authors: ME
authors: Ketelaar
authors: University Medical Center Groningen, Department of Pathology and Medical Biology, Laboratory of Allergology and Pulmonary Diseases, University of Groningen, Groningen, The Netherlands.
authors: M C
authors: MC
authors: Nawijn
authors: Division of Respiratory Medicine, University of Nottingham, Nottingham, UK.
authors: D E
authors: DE
authors: Shaw
authors: University Medical Center Groningen, Pediatric Pulmonology and Pediatric Allergology, Beatrix Children's Hospital, Groningen Research Institute for Asthma and COPD, University of Groningen, Groningen, The Netherlands.
authors: G H
authors: GH
authors: Koppelman
authors: Division of Respiratory Medicine, University of Nottingham, Nottingham, UK.
authors: I
authors: I
authors: Sayers
mesh_terms: D001249:Asthma / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards; D006801:Humans; D000067596:Interleukin-33 / Q000097:blood*; D011933:Reagent Kits, Diagnostic / Q000592:standards; D015203:Reproducibility of Results
chemical_list: D000067596:Interleukin-33; D011933:Reagent Kits, Diagnostic
keywords: IL-1RL1; IL-33; asthma; immunoassay; interference; sensitivity; serum; specificity