Journal d'immunologie clinique et cellulaire
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Abstrait

Peripheral Blood B cell Subsets and BAFF/APRIL Levels and their Receptors are Disturbed in Rheumatoid Arthritis but not in Ankylosing Spondylitis

Beatrice Gaugler, Caroline Laheurte, Ewa Bertolini, Aurore Pugin, Daniel Wendling, Philippe Saas, Eric Toussirot on behalf of CBT-506

Background: To evaluate the distribution of circulating B cell subsets and their expression of BAFF/APRIL receptors (BAFF-R, TACI and BCMA) as well as circulating levels of BAFF and APRIL in patients with rheumatoid arthritis (RA) or ankylosing spondylitis (AS) compared to healthy controls (HC).
Methods: 59 patients with RA, 61 patients with AS and 61 HC were evaluated. All patients were receiving traditional treatments and had not received prior biological treatment. Peripheral blood B cell subsets were assessed using multicolor flow cytometry using CD27, CD38 and IgD staining. Expression of BAFF-R, TACI and BCMA was analyzed on each cell subset.
Results: Distribution of peripheral B cells subsets was disturbed in RA compared to HC, with a decreased proportion of naïve and transitional B cells (p<0.005), whereas B cell subsets were comparable between AS and HC. Circulating BAFF did not differ between the three groups, while the ratio of BAFF/B cell number was significantly higher in RA compared to HC (p<0.001). Circulating APRIL levels were increased in RA compared to HC (p<0.001). Circulating BAFF and APRIL, and BAFF/B cell ratio did not differ between AS and HC. We also observed increased expression of BCMA, but not BAFF-R in RA, on both naïve and memory B cell subsets (post germinal center) (p<0.005), whereas TACI expression was decreased on memory B cells (p=0.001). The expression of BAFF/APRIL receptors did not differ between AS and HC.
Conclusion: Disturbances in B cell homeostasis in RA may promote B cell survival and deregulation, favoring the emergence of autoimmune B cells. Conversely, B cell homeostasis is not disrupted in AS.