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Identification of IgG3-specific epitope that remedies problem in diagnostic IgG subclass determination due to human genetic variation
  1. Heather L Howie1,
  2. Xiaohong Wang1,
  3. Linda Kapp1,
  4. Jenna N Lebedev1,
  5. James C Zimring1,2,3
  1. 1 Bloodworks NW Research Institute, Seattle, Washington, USA
  2. 2 Department of Laboratory Medicine, University of Washington, Seattle, Washington, USA
  3. 3 Department of Internal Medicine, Division of Hematology, University of Washington, Seattle, Washington, USA
  1. Correspondence to Dr James C Zimring, Bloodworks NW Research Institute, 1551 Eastlake Ave E, Seattle, WA 98102, USA; jzimring{at}


There are four subtypes of human IgG with different effector functions. Quantifying the relative amount of each IgG subtype is important for laboratory diagnosis in multiple settings. However, in an evolving landscape of the appreciation of human variability and the need for precision/personalised laboratory diagnosis, it has also been shown that there are numerous natural variants of IgG subtypes, with at least 29 having been described. It has recently been reported that commercially available polyclonal antisera to IgG3 cross react with variants of other IgG subtypes, while available monoclonal anti-IgG3 have a blind-spot for the IgG3-04 variant. Herein, we report that IgG3-04 contains an epitope in common with all known IgG3 variants and absent in other subtypes. A novel monoclonal anti-IgG3 is described that is specific to IgG3 but without any blind-spots for known IgG3 variants, providing a remedy to the problem of genetic variability of IgG3.

  • immunoglobulin
  • immunohistochemistry
  • antigenic epitopes

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  • Handling editor Stephen R A Jolles.

  • Contributors JCZ and HLH conceived of the experiments, analysed data and wrote the manuscript. HLH, XW, LK and JNL carried out the described experiments and analysed data.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests Bloodworks NW has filed intellectual properties around the PUMA1 reagents in this report- HLH, LK, JNL and JCZ and are each employees of Bloodworks NW. XW has no competing interests to declare.

  • Provenance and peer review Not commissioned; externally peer reviewed.