title: C1q-fixing human leukocyte antigen assay in immunized renal patients: correlation between Luminex SAB-C1q and SAB-IgG.
abstract: BACKGROUND
  There is no consensus about the impact of thresholds of complement-fixing antibody assays. Recently, a C1q-SAB assay has been developed to identify complement-fixing HLA antibodies with high sensitivity and specificity. Our aim was to determine the correlation between IgG single antigens beads (SAB) and C1q-SAB assay results among patients on the renal waiting list.
  
  
  METHODS
  Serum samples from immunized renal waiting list patients as well as negative and positive controls were valided by Luminex (LMX). These sera, which were positive for 166 antibody specificities, were tested for HLA class I in parallel by LMX-IgG and LMX-C1q.
  
  
  RESULTS
  Comparison of antibody detection revealed no correlation based on median fluorescent intensity (MFI), levels between the IgG SAB and the C1qSAB assay (P > .05). IgG-positive sera with MFIs as low as 700 were able to fix C1q, whereas other sera with MFIs as high 14,500 did not. Furthermore, there appeared to be disparities in the profiles of class I antigens able to fix C1q-SAB. In our series, only 34% class I IgG SAB antibodies were also C1qSAB+. In several patients, we detected C1qSAB+ against IgGSAB- that was surely due to IgM antibodies. So, the C1qSAB assay detected IgM antibodies that fix complement.
  
  
  CONCLUSIONS
  These data suggested that the C1q-SAB assay could be an important method to evaluate pretransplant virtual crossmatch and to define nonpermitted specificities (C1q-fixing) in kidney transplantation.
authors.affiliation: Department of Nephrology, University Hospital Virgen Arrixaca, Murcia, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Llorente
authors.forename: F
authors.initials: F
authors.lastname: Boix
authors.forename: J
authors.initials: J
authors.lastname: Eguia
authors.forename: M
authors.initials: M
authors.lastname: López
authors.forename: A
authors.initials: A
authors.lastname: Bosch
authors.forename: H
authors.initials: H
authors.lastname: Martinez
authors.forename: M J
authors.initials: MJ
authors.lastname: Gonzalez
authors.forename: R
authors.initials: R
authors.lastname: López-Hernández
authors.forename: G
authors.initials: G
authors.lastname: Salgado
authors.forename: M R
authors.initials: MR
authors.lastname: Moya-Quiles
authors.forename: J A
authors.initials: JA
authors.lastname: Campillo
authors.forename: A M
authors.initials: AM
authors.lastname: García-Alonso
authors.forename: A
authors.initials: A
authors.lastname: Minguela
authors.forename: L
authors.initials: L
authors.lastname: Jimeno
authors.forename: M R
authors.initials: MR
authors.lastname: Alvarez-López
authors.forename: M
authors.initials: M
authors.lastname: Muro
mesh_terms: D016009:Chi-Square Distribution; D015922:Complement C1q / Q000276:immunology*; D003168:Complement Fixation Tests; D006084:Graft Rejection / Q000276:immunology / Q000517:prevention & control; D006680:HLA Antigens / Q000276:immunology*; D006648:Histocompatibility; D006650:Histocompatibility Testing / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007518:Isoantibodies / Q000097:blood*; D007674:Kidney Diseases / Q000175:diagnosis / Q000276:immunology* / Q000601:surgery; D016030:Kidney Transplantation / Q000276:immunology; D007962:Leukocytes / Q000276:immunology*; D011237:Predictive Value of Tests; D018570:Risk Assessment; D012307:Risk Factors; D016896:Treatment Outcome; D014850:Waiting Lists
chemical_list: D006680:HLA Antigens; D007074:Immunoglobulin G; D007518:Isoantibodies; D015922:Complement C1q