TY - JOUR T1 - Plasmablasts as a biomarker for IgG4-related disease, independent of serum IgG4 concentrations JF - Annals of the Rheumatic Diseases JO - Ann Rheum Dis SP - 190 LP - 195 DO - 10.1136/annrheumdis-2014-205233 VL - 74 IS - 1 AU - Zachary S Wallace AU - Hamid Mattoo AU - Mollie Carruthers AU - Vinay S Mahajan AU - Emanuel Della Torre AU - Hang Lee AU - Maria Kulikova AU - Vikram Deshpande AU - Shiv Pillai AU - John H Stone Y1 - 2015/01/01 UR - http://ard.bmj.com/content/74/1/190.abstract N2 - 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. ER -