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Extended report
Plasmablasts as a biomarker for IgG4-related disease, independent of serum IgG4 concentrations
  1. Zachary S Wallace1,
  2. Hamid Mattoo2,
  3. Mollie Carruthers1,
  4. Vinay S Mahajan2,
  5. Emanuel Della Torre2,
  6. Hang Lee3,
  7. Maria Kulikova2,
  8. Vikram Deshpande4,
  9. Shiv Pillai2,
  10. John H Stone1
  1. 1Division of Rheumatology, Allergy, and Immunology, Massachusetts General Hospital, Boston, Massachusetts, USA
  2. 2Massachusetts General Hospital Cancer Center, Boston, Massachusetts, USA
  3. 3Biostatistics Center, Massachusetts General Hospital, Boston, Massachusetts, USA
  4. 4Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts, USA
  1. Correspondence to Dr John H Stone, Rheumatology Clinic/Yawkey 2, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA; jhstone{at}


Objectives We examined the utility of circulating total and IgG4+ plasmablasts as biomarkers of diagnosis and disease activity in IgG4-related disease (IgG4-RD).

Materials methods We evaluated patients with active, untreated, biopsy-proven IgG4-RD affecting various organs. Flow cytometry was used to measure total plasmablast and IgG4+ plasmablast counts by gating peripheral blood for CD19lowCD38+CD20−CD27+ cells and CD19lowCD38+CD20−CD27+IgG4+ cells. Serum IgG4 concentrations were measured by nephelometry. We compared 37 IgG4-RD patients to 35 controls, including healthy individuals (n=14) and patients with other inflammatory diseases before treatment (n=21).

Results The IgG4-RD patients’ mean age was 59, and 68% were male. Fourteen patients (38%) had three or more organs involved. The IgG4-RD patients had substantially elevated total plasmablast counts (median 4698/mL, range 610–79524/mL) compared to both untreated disease controls (median 592/mL, range 19–4294/mL; p < 0.001) and healthy controls (median 94/mL, range 1–653/mL; p < 0.001). Thirteen IgG4-RD patients (36%) had normal serum IgG4 concentrations (mean 60 mg/dL, range 5–123 mg/dL, normal <135 mg/dL). However, the median plasmablast count was not significantly lower in that subset with normal serum IgG4 concentrations (3784/mL) compared to those with elevated serum IgG4 (5155/mL) (p = 0.242). Among the 12 rituximab (RTX)-treated patients, the median plasmablast level during disease flare was 6356/mL (range 1123–41589/mL), declining to 1419/mL (range 386/mL–4150/mL) during remission (p < 0.01).

Conclusions Circulating plasmablasts are elevated in active IgG4-RD, even in patients with normal serum IgG4 concentrations. Plasmablast counts are a potentially useful biomarker for diagnosis, assessing response to treatment, and determining the appropriate time for re-treatment.

  • B cells
  • Disease Activity
  • Treatment

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