Background B-cell monitoring has been extensively used in patients (pts) with rheumatoid arthritis (RA) to assess the efficacy of biologic therapy and the relationship between B-cell recovery and clinical outcomes.
Objectives To evaluate the B-cell subsets in peripheral blood of RA pts treated with rituximab (RTX) and tocilizumab (TCZ).
Methods 18 pts with active refractory RA were assessed at baseline and at weeks 12 and 24 for clinical and laboratory data. 10 pts: 8F/2M; median age 58 years (47-62); disease duration 6 years (3-20) received RTX and 8 pts: 6F/2M, median age 45.5 years (38-61); disease duration 14 years (7-19) – TCZ in the standard therapeutic dosage. Pts of both groups were treated with DMARDs, glucocorticoids, and NSAIDS. At baseline, DAS28 was 5.1 (4-5.8) and 5.5 (5.2-6.5); 90% (9 pts) and 62.5% (8 pts) were both RF and anti-CCP positive in RTX and TCZ group, respectively, with no difference between the groups. CD19+ B cells, memory B cells (CD19+CD27-), non-switched (CD19+IgD+CD27+) and switched memory B cells (CD19+IgD-CD27+), naïve (CD19+IgD+CD27-), transitional (CD19+IgD+CD10+CD38++CD27-) B cells, and plasmablasts (CD19+CD38+++IgD-CD27+CD20) were analyzed using multicolor flow cytometry.
Results At baseline, the median percentages of memory B cells (CD19+CD27-) and non-switched memory B-cells (CD19+CD27+IgD+) were lower in RA cohort compared to healthy donors (n=27): 1.55% (1.1-2.1) versus 2.2% (1.6-3.3), p=0.028 and 6.2% (2.7-11.1) versus 10% (6.4-12.7), p=0.035, respectively. The percentage of memory B cells (CD19+CD27-) correlated positively (r=0.52) with ESR and negatively (r=-0.49) with the age of the patients, p<0.05 for both cases. There was no difference in the frequencies of B-cell subsets between RTX and TCZ group. At 12 and 24 weeks, DAS28 decreased significantly in RTX group, median 3.2 (2.7-4.2) and 3.4 (2.7-4.1) and TCZ group, median 4.2 (3.5-4.7) and 3.1 (2.9-3.5), p<0.05 for all cases. In RTX group, the complete depletion of CD19+ B cells and memory B cells was seen in all but 1 patient at 12 and 24 weeks. At week 24 of RTX treatment, repopulation occurred mainly with switched memory B cells, median 11.8% (0-31), non-switched, median 1.85% (0-8.15), and naïve B cells, median 3.05% (0-17.5). In TCZ group, the frequency of CD19+ B cells and memory B cells remained stable (median 5.3% (2.5-7.6) and 1.4% (1.2-1.6) at baseline, 3.9% (2.9-7.1) and 1.6% (1.2-1.9) at week 12, 4.2% (3.3-5.3) and 1.1% (0.8-1.1) at week 24, respectively). Transitional cells decreased from a median 0.1%, (0.05-0.1) at baseline to a median 0%, (0-0), p=0.043 after week 12; other B-cell subsets have not changed during the study.
Conclusions The decreased frequencies of memory B cells (CD19+CD27-) and non-switched memory B cells (CD19+CD27+IgD+) were found in RA patients compared to healthy donors. RTX induced a profound depletion of all peripheral CD 19+ B-cell subsets in RA patients. During TCZ therapy, the frequencies of transitional cells decreased at week 12. No significant influence of TCZ was found on other B-cell subsets.
Acknowledgements The authors thank Prof. H.-P. Tony, A. Koss-Kinzinger, and Z. Mahmood (University of Wuerzburg, Germany) for the assistance in the analysis of preliminary results.
Disclosure of Interest None declared