RT Journal Article
SR Electronic
T1 Longterm Effects of Rituximab on B Cell Counts and Autoantibody Production in Rheumatoid Arthritis: Use of High-sensitivity Flow Cytometry for More Sensitive Assessment of B Cell Depletion
JF The Journal of Rheumatology
JO J Rheumatol
FD The Journal of Rheumatology
SP jrheum.111488
DO 10.3899/jrheum.111488
A1 Andrea Váncsa
A1 Zoltán Szabó
A1 Szilvia Szamosi
A1 Nóra Bodnár
A1 Edit Végh
A1 Lajos Gergely
A1 Gabriella Szűcs
A1 Sándor Szántó
A1 Zoltán Szekanecz
YR 2013
UL http://www.jrheum.org/content/early/2013/03/25/jrheum.111488.abstract
AB Objective To assess the efficacy and safety of longterm rituximab (RTX) therapy for rheumatoid arthritis (RA) and study correlations among B cell depletion, clinical response, and autoantibody production. Methods Seventy-seven patients with moderate or high RA activity received RTX and were re-treated every 6 months regardless of clinical response. All patients received at least 5 cycles. We assessed 28-joint Disease Activity Score (DAS28), IgM rheumatoid factor (RF), and anticitrullinated protein antibody (ACPA) levels at baseline, after 15 days, and then every 6 months for 24 months. Absolute CD19+ B lymphocyte counts were determined in 50 patients using high-sensitivity flow cytometry (hsFACS) by reading 100,000 events. Results After 6, 12, 18, and 24 months, 51.6%, 51.9%, 73.3%, and 83.8% of patients, respectively, showed good European League Against Rheumatism responses. Significant and sustained decreases in IgM RF and ACPA levels were observed as early as 6 months and 12 months, respectively. The baseline mean absolute B cell number was 0.234 g/l. B cell numbers diminished significantly after the very first infusion by Day 15 (0.104 g/l; p = 0.007); they further decreased until 24 months (0.0013 g/l; p < 0.001). One RTX infusion resulted in incomplete depletion in 76.7% of patients. Upon RTX treatment, changes in CD19+ B cell numbers positively correlated with changes in DAS28 (r = 0.963, p = 0.008) and IgM RF (r = 0.859, p = 0.028), but not with changes in ACPA production (r = 0.726, p = 0.102). The correlations between B cell numbers and DAS28 were observed in both ACPA-seropositive (r = 0.999, p < 0.0001) and ACPA-negative patient subpopulations (r = 0.962, p = 0.009). The correlation between CD19+ cell numbers and IgM RF was observed only in the ACPA-positive population (r = 0.944, p = 0.005) but not in seronegative patients (r = 0.398, p = 0.435). No safety issues arose. Conclusion In RA, clinical response to RTX is associated with the extent of B cell depletion and with autoantibody production. Changes in CD19+ B cell numbers correlate with those in disease activity and, in seropositive patients, also with IgM RF, but not with ACPA production. We found that hsFACS may be a useful method to more accurately assess incomplete B cell depletion.