title: Serum IgG2 and tissue IgG2 plasma cell elevation in orbital IgG4-related disease (IgG4-RD): Potential use in IgG4-RD assessment.
abstract: To determine the role of serum and tissue IgG2 in orbital biopsies with the histological features of IgG4-related disease (IgG4-RD) in comparison with non-IgG4-related orbital inflammatory disorders (OID), including autoimmune disorders.
  
  
  
  This is an international (Sheffield, UK, and Singapore) collaborative, retrospective case review of 69 patients (38 from Singapore National Eye Centre and 31 from Royal Hallamshire Hospital, Sheffield) with orbital inflammatory biopsies between 2002 and 2016. Clinical information and histology were reviewed and cases were classified into three groups: Group 1: IgG4-RD orbital inflammation (n=43); Group 2: idiopathic OID (n=12) and Group 3: autoimmune OID (n=14). Serum IgG1, IgG2, IgG3 and IgG4 levels were collated where available and immunohistochemistry (IHC) for tissue IgG2 plasma cells was performed.
  
  
  
  Dual IHC showed IgG2 plasma cells as a distinct population from IgG4 plasma cells. Significant (twofold) serum IgG2 elevation was noted among IgG4-RD (group 1), idiopathic (group 2) and autoimmune OID (group 3). Similarly, significant elevation of tissue IgG2 plasma cells was also seen among IgG4-RD (group 1), idiopathic and autoimmune OID (groups 2 and 3).
  
  
  
  Significant elevations of serum IgG2 and tissue IgG2 plasma cells are present in orbital IgG4-RD in comparison with non-IgG4 orbital inflammation (idiopathic and autoimmune OID), suggesting that IgG2 may play a role in IgG4-RD. A serum IgG2 cut-off >5.3 g/L was found to be 80% sensitive and 91.7% specific for orbital IgG4-RD, with an accuracy of 0.90. Tissue IgG2 and IgG4 subclass reporting may provide additional insight regarding the 'IgG4-RD' pathogenesis.
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Department of Anatomical Pathology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Anita S Y
authors.initials: ASY
authors.lastname: Chan
authors.affiliation: Department of Histopathology, Royal Hallamshire Hospital, National Specialist Ophthalmic Pathology Service (NSOPS), Sheffield, UK.
authors.forename: Hardeep
authors.initials: H
authors.lastname: Mudhar
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Sunny Yu
authors.initials: SY
authors.lastname: Shen
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Stephanie S
authors.initials: SS
authors.lastname: Lang
authors.affiliation: Department of Histopathology, Singapore General Hospital, Singapore.
authors.forename: Malee
authors.initials: M
authors.lastname: Fernando
authors.affiliation: Department of Anatomical Pathology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Maryam Hazly
authors.initials: MH
authors.lastname: Hilmy
authors.affiliation: Department of Advanced Diagnostics, University College London, London, UK.
authors.forename: Naomi Jayne
authors.identifier: 0000-0003-1004-3605
authors.initials: NJ
authors.lastname: Guppy
authors.affiliation: Academic Unit of Ophthalmology and orthoptics, University of Sheffield, Royal Hallamshire Hospital, Sheffield, UK.|Department of Oncology, University of Sheffield, Royal Hallamshire Hospital, Sheffield, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Rennie
authors.affiliation: Department of Rheumatology, Royal Hallamshire Hospital, Sheffield, UK.
authors.forename: Lisa
authors.initials: L
authors.lastname: Dunkley
authors.affiliation: Department of Anatomical Pathology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Issam
authors.initials: I
authors.lastname: Al Jajeh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000175:diagnosis / Q000276:immunology / Q000378:metabolism*; D001706:Biopsy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009915:Orbit / Q000378:metabolism / Q000473:pathology*; D016727:Orbital Pseudotumor / Q000175:diagnosis / Q000276:immunology / Q000378:metabolism*; D010950:Plasma Cells / Q000276:immunology / Q000378:metabolism*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D007074:Immunoglobulin G
keywords: IgG2; IgG4; IgG4-related disease (IgG4-RD); orbital inflammatory disorders (OID)