title: A new blood group antigen is defined by anti-CD59, detected in a CD59-deficient patient.
abstract: BACKGROUND
  CD59 is a cell surface glycoprotein of approximately 20 kDa limiting the lytic activity of the terminal complement complex C5b-9. Although CD59 is known as a red blood cell (RBC) antigen defined by monoclonal antibodies, it so far has not been identified as a blood group antigen, since the description of a human alloantibody was missing. In this study we show the presence of an anti-CD59 in a patient affected by a homozygous CD59 deficiency.
  
  
  METHODS
  RBC CD59 and CD55 were determined by flow cytometry or by the column agglutination technique using monoclonal antisera. Commercially available His-tagged recombinant soluble CD59 protein was used to inhibit anti-CD59.
  
  
  RESULTS
  Seven cases of an isolated CD59 deficiency due to three distinct null alleles of the CD59 gene have been published so far. Recently we described the CD59-null allele c.146delA in a young child of heterozygous parents. Her plasma contained an alloantibody directed against the high-prevalence RBC antigen CD59. The antibody specificity was identified using soluble recombinant human CD59 protein, which blocked the reactivity of the patient's antibody and of monoclonal anti-CD59 but not of monoclonal anti-CD55. In addition, RBC alloantibodies such as anti-K, anti-C, anti-c, or anti-Fy(a) remained unaffected. Therefore, inhibition by recombinant CD59 is a useful diagnostic tool to detect alloantibodies in the presence of anti-CD59.
  
  
  CONCLUSIONS
  This is the first demonstration of a human anti-CD59 alloantibody, which defines CD59 as an RBC blood group antigen. CD59 represents a candidate for a new blood group system.
authors.affiliation: Institute of Clinical Transfusion Medicine and Immunogenetics Ulm, German Red Cross Blood Transfusion Service Baden-Württemberg-Hessen, Ulm, Germany; Institute of Transfusion Medicine, University of Ulm, Ulm, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Anliker
authors.forename: Inge
authors.initials: I
authors.lastname: von Zabern
authors.forename: Britta
authors.initials: B
authors.lastname: Höchsmann
authors.forename: Henriette
authors.initials: H
authors.lastname: Kyrieleis
authors.forename: Christian
authors.initials: C
authors.lastname: Dohna-Schwake
authors.forename: Willy A
authors.initials: WA
authors.lastname: Flegel
authors.forename: Hubert
authors.initials: H
authors.lastname: Schrezenmeier
authors.forename: Christof
authors.initials: C
authors.lastname: Weinstock
mesh_terms: D000743:Anemia, Hemolytic / Q000235:genetics / Q000276:immunology*; D001789:Blood Group Antigens / Q000235:genetics / Q000276:immunology*; D018957:CD59 Antigens / Q000235:genetics / Q000276:immunology*; D002675:Child, Preschool; D005260:Female; D016368:Frameshift Mutation; D006456:Hemoglobinuria / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007518:Isoantibodies / Q000097:blood*
chemical_list: D001789:Blood Group Antigens; D018957:CD59 Antigens; D007518:Isoantibodies; C051590:CD59 protein, human