title: Immune complexome analysis of serum and its application in screening for immune complex antigens in rheumatoid arthritis.
abstract: BACKGROUND
  Analysis of circulating immune complexes (CICs) produced during an immune response may be useful in elucidating some aspects of this process. Identification of antigens incorporated into CICs provides information that may be helpful in developing diagnostic and treatment strategies for autoimmune diseases, infection, cancer, and transplantation therapy, and such information might be more relevant than information on free antigens. Because CICs may contain many antigens, comprehensive identification and profiling of such antigens is more effective than immunoblotting detection.
  
  
  METHODS
  We developed a novel proteomic strategy (immune complexome analysis) in which immune complexes (ICs) are separated from serum, digested directly with trypsin, and then subjected to nano-liquid chromatography-tandem mass spectrometry for identifying and profiling antigens in CICs. We applied this strategy to the analysis of CICs in 21 rheumatoid arthritis (RA) patients. Serum samples from 13 healthy donors and 8 osteoarthritis patients were used as controls.
  
  
  RESULTS
  CICs containing thrombospondin-1 (TSP-1) and platelet factor 4 (PF4) were found in the serum of 81% and 52% of RA patients, respectively, and in none of the controls.
  
  
  CONCLUSIONS
  The ICs in the serum of a majority of the RA patients contained TSP-1 or PF4, and these ICs may have potential as alternative biomarkers. Our technique for immune complexome analysis uses routine clinical samples, simple protocols, and widely available equipment. This method may be generally applicable to the study of the relationship between CICs and certain diseases associated with the immune response in animals and humans.
authors.affiliation: Department of Environmental and Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Kaname
authors.initials: K
authors.lastname: Ohyama
authors.forename: Yukitaka
authors.initials: Y
authors.lastname: Ueki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kawakami
authors.forename: Naoya
authors.initials: N
authors.lastname: Kishikawa
authors.forename: Mami
authors.initials: M
authors.lastname: Tamai
authors.forename: Makoto
authors.initials: M
authors.lastname: Osaki
authors.forename: Shimeru
authors.initials: S
authors.lastname: Kamihira
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Nakashima
authors.forename: Naotaka
authors.initials: N
authors.lastname: Kuroda
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000936:Antigen-Antibody Complex / Q000097:blood* / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D002853:Chromatography, Liquid; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D036103:Nanotechnology; D010978:Platelet Factor 4 / Q000097:blood / Q000276:immunology; D020543:Proteome / Q000032:analysis* / Q000276:immunology; D053719:Tandem Mass Spectrometry; D019700:Thrombospondin 1 / Q000097:blood / Q000276:immunology
chemical_list: D000936:Antigen-Antibody Complex; D015415:Biomarkers; D020543:Proteome; D019700:Thrombospondin 1; D010978:Platelet Factor 4