title: Serological blind spots for variants of human IgG3 and IgG4 by a commonly used anti-immunoglobulin reagent.
abstract: Human immunoglobulin G (IgG) includes four different subtypes (IgG1, IgG2, IgG3, and IgG4), and it is also now appreciated that there are genetic variations within IgG subtypes (called isoallotypes). Twenty-nine different isoallotypes have been described, with 7, 4, 15, and 3 isoallotypes described for IgG1, IgG2, IgG3, and IgG4, respectively. The reactivity of anti-IgG with different isoallotypes has not been characterized.
  
  
  
  A novel monoclonal anti-K antibody (PugetSound Monoclonal Antibody 1 [PUMA1]) was isolated and sequenced, and a panel of PUMA1 variants was expressed, consisting of the 29 known IgG isoallotypes. The resulting panel of antibodies was preincubated with K-positive red blood cells (RBCs) and then subjected to testing with currently approved anti-IgG by flow cytometry, solid phase systems, gel cards, and tube testing.
  
  
  
  A US Food and Drug Administration (FDA)-approved monoclonal anti-IgG (gamma-clone) failed to recognize 2 of 15 IgG3 isoallotypes (IgG3-03 and IgG3-13) and 3 of 3 IgG4 isoallotypes (IgG4-01, IgG4-02, and IgG4-03). In contrast, an FDA-approved rabbit polyclonal anti-IgG recognized each of the known human IgG isoallotypes.
  
  
  
  These findings demonstrate "blind spots" in isoalloantibody detection by a monoclonal anti-IgG. If a patient has anti-RBC antibodies predominantly of an IgG3 subtype (the IgG3-03 and/or IgG3-13 variety), then it is possible that a clinically significant alloantibody would be missed. IgG-03 and IgG-13 have an estimated frequency of 1% to 3% in Caucasian populations and 20% to 30% in certain African populations. Nonreactivity with IgG4 is a known characteristic of this monoclonal anti-IgG, but IgG4 isoallotypes have not been previously reported.
authors.affiliation: BloodworksNW Research Institute.
authors.forename: Heather L
authors.initials: HL
authors.lastname: Howie
authors.affiliation: BloodworksNW Research Institute.|Departments of Laboratory Medicine and Internal Medicine, Division of Hematology, University of Washington, Seattle, Washington.
authors.forename: Meghan
authors.initials: M
authors.lastname: Delaney
authors.affiliation: BloodworksNW Research Institute.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.affiliation: BloodworksNW Research Institute.
authors.forename: Lay See
authors.initials: LS
authors.lastname: Er
authors.affiliation: Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Gestur
authors.initials: G
authors.lastname: Vidarsson
authors.affiliation: Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Tamara C
authors.initials: TC
authors.lastname: Stegmann
authors.affiliation: BloodworksNW Research Institute.
authors.forename: Linda
authors.initials: L
authors.lastname: Kapp
authors.affiliation: BloodworksNW Research Institute.
authors.forename: Jenna N
authors.initials: JN
authors.lastname: Lebedev
authors.affiliation: BloodworksNW Research Institute.
authors.forename: Yanyun
authors.initials: Y
authors.lastname: Wu
authors.affiliation: BloodworksNW Research Institute.|Departments of Laboratory Medicine and Internal Medicine, Division of Hematology, University of Washington, Seattle, Washington.
authors.forename: James P
authors.identifier: 0000-0002-7976-6871
authors.initials: JP
authors.lastname: AuBuchon
authors.affiliation: BloodworksNW Research Institute.|Departments of Laboratory Medicine and Internal Medicine, Division of Hematology, University of Washington, Seattle, Washington.
authors.forename: James C
authors.initials: JC
authors.lastname: Zimring
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000276:immunology*; D003951:Diagnostic Errors; D014644:Genetic Variation; D006801:Humans; D007126:Immunoglobulin Allotypes / Q000276:immunology*; D007074:Immunoglobulin G / Q000032:analysis* / Q000235:genetics; D011817:Rabbits; D044469:Racial Groups
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D007126:Immunoglobulin Allotypes; D007074:Immunoglobulin G; C048844:anti-IgG