title: Elevated serum IgG4 defines specific clinical phenotype of rheumatoid arthritis.
abstract: OBJECTIVE
  To explore the correlation of serum IgG4 (sIgG4) with clinical manifestations or therapeutic response in rheumatoid arthritis (RA).
  
  
  METHODS
  Consecutive 136 RA patients were recruited and followed up at regular interval. SIgG4 was detected by immunonephelometry. Serial synovial tissue sections from 46 RA patients were stained immunohistochemically for IgG4.
  
  
  RESULTS
  Forty-six percent of 136 RA patients had elevated sIgG4. Patients with elevated sIgG4 had higher sIgG4/sIgG ratio, C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, and anticyclic citrullinated peptide antibodies than those with normal sIgG4 (all P < 0.05). Among 45 patients who received methotrexate and leflunomide therapy, 50% (9/18) of patients with elevated sIgG4 and 85% (23/27) of patients with normal sIgG4 reached therapeutic target (disease activity score of 28 joints < 3.2) at 6-month visit (χ(2) = 6.508, P = 0.011). IgG4-positive plasma cell count correlated positively with sIgG4, total synovitis score, and CD3-, CD20-, and CD38-positive cell counts (all P < 0.05).
  
  
  CONCLUSIONS
  Our results showed that elevated sIgG4 in RA is common and disproportional to total IgG and RA with elevated sIgG4 may be a specific clinical phenotype with higher disease activity, higher level of autoantibodies, and poor response to methotrexate and leflunomide therapy.
authors.affiliation: Department of Rheumatology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, No. 107 Yan Jiang West Road, Guangzhou 510120, China.
authors.forename: Le-Feng
authors.identifier: 0000-0002-2902-3922
authors.initials: LF
authors.lastname: Chen
authors.affiliation: Department of Rheumatology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, No. 107 Yan Jiang West Road, Guangzhou 510120, China.
authors.forename: Ying-Qian
authors.initials: YQ
authors.lastname: Mo
authors.affiliation: Department of Rheumatology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, No. 107 Yan Jiang West Road, Guangzhou 510120, China.
authors.forename: Jian-Da
authors.initials: JD
authors.lastname: Ma
authors.affiliation: Department of Clinical Laboratory, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, No. 107 Yan Jiang West Road, Guangzhou 510120, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Luo
authors.affiliation: Department of Rheumatology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, No. 107 Yan Jiang West Road, Guangzhou 510120, China.
authors.forename: Dong-hui
authors.initials: DH
authors.lastname: Zheng
authors.affiliation: Department of Rheumatology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, No. 107 Yan Jiang West Road, Guangzhou 510120, China.
authors.forename: Lie
authors.initials: L
authors.lastname: Dai
mesh_terms: D051997:ADP-ribosyl Cyclase 1 / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018951:Antigens, CD20 / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000097:blood*; D001323:Autoantibodies / Q000097:blood; D001706:Biopsy; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000378:metabolism; D017252:CD3 Complex / Q000378:metabolism; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000097:blood; D010641:Phenotype; D012217:Rheumatoid Factor / Q000097:blood; D013582:Synovial Fluid / Q000378:metabolism; D013585:Synovitis / Q000378:metabolism; D055815:Young Adult
chemical_list: D018951:Antigens, CD20; D001323:Autoantibodies; D017252:CD3 Complex; D007074:Immunoglobulin G; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D002097:C-Reactive Protein; D012217:Rheumatoid Factor; D051997:ADP-ribosyl Cyclase 1