Background Alterations of B-cell subpopulation have been described in the peripheral blood of rheumatoid arthritis (RA) patients (pts), but differences between B-cell subsets distributions in early and late onset RA (LORA) are still unclear [1,2].

Objectives To examine B-cell subsets in peripheral blood of healthy donors, early (disease duration <6 months) RA (ERA) and LORA pts by flow cytometry, and to analyze the association between B-cell subsets and RA activity.

Methods 24 active ERA pts (20F/4M); median age 54 years (range) (38–64); disease duration 5 months (4–6); DAS28 score 5.2 (4.7–5.9); RF+75%, ACCP+ 87.5% and 20 LORA pts (16F/4M); median age 58 years (range) (44–62); disease duration 12 years (4.5–17.5); DAS28 score 5.3 (4.6–6.2); both RF+ and ACCP+ 80%, were assessed for B-cell subpopulations and laboratory data: ESR, CRP. LORA pts were treated with DMARDs (anti-TNF-α, Methotrexate), glucocorticoids, and NSAIDS; ERA pts received NSAIDS only. CD19+B cells, memory B cells (CD19+CD27-), non-switched memory B cells (CD19+IgD+CD27+), switched memory B cells (CD19+IgD-CD27+), naïve (CD19+IgD+CD27-), double-negative (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 The median percentages (range) of non-switched memory B cells (CD19+IgD+CD27+) were lower in ERA and LORA RA cohorts compared to donors: 3.0% (1.6–5.5) and 6.2% (2.4–10.2) vs 7.4% (3.7–11.1), respectively, p<0.05 for both cases. In LORA pts, the median percentages (range) and absolute numbers of switched memory B cells (CD19+IgD+CD27-) were higher compared to both ERA pts and donors: 24,1% (14,0–42.3) vs 8,3% (4.4–12.9) and 12.8% (9.3–17.0); and 0.03 (0.02–0.05) vs 0.01 (0.006–0.02) and 0.02 (0.01–0.04), respectively; p<0.05 for all cases. The median percentages of naïve B cells (CD19+IgD+CD27-) were significantly higher in ERA pts compared to LORA pts and healthy donors: 75.3% (69.7–83.6) vs 54.3% (39.7–69.1) and 64.7% (57.6–72.4), respectively, p<0.05 for both cases.

In ERA pts, we found a significant correlation between absolute numbers of non-switched memory B cells (CD19+IgD+CD27+), RF and anti-CCP: r=0.50 and 0.45, respectively, p<0.05 for both cases. In LORA pts, the percentage of memory B cells (CD19+CD27+) correlated positively with ESR (r=0.58), p<0.05; a positive association was observed between the absolute numbers of switched memory B cells (CD19+IgD-CD27+), CRP (r=0.48) and RF (r=0.49), p<0.05 for all cases.

Conclusions in ERA pts, immunophenotyping showed increased frequencies of naïve B cells and decreased frequencies and absolute numbers of switched memory B cells compared to LORA cohort.

References

1. Fedele et al. BMC Immunology 2014, 15:28. doi: 10.1186/s12865-014-0028-1. Memory B cell subsets and plasmablasts are lower in early than in long-standing Rheumatoid Arthritis.

2. Moura RA et al. Rheumatology 2010 Jun;49(6):1082–92. doi: 10.1093/rheumatology/keq029. Alterations on peripheral blood B-cell subpopulations in very early arthritis patients.

References

Disclosure of Interest None declared