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

doi:10.4172/2155-9899.1000163

Abstract

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 naive 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 naive 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.

Highlights

The involvement of B cells in systemic autoimmune diseases has emerged as a new concept over the past ten years, leading to new avenues for innovative therapeutic strategies
B cell homeostasis is not disrupted in ankylosing spondylitis (AS)
Since there was a decrease in B cells in rheumatoid arthritis (RA) patients, we examined the ratio of circulating BAFF to total B cell count

Summary

Introduction

The involvement of B cells in systemic autoimmune diseases has emerged as a new concept over the past ten years, leading to new avenues for innovative therapeutic strategies. B cells play a number of critical roles in inducing and perpetuating autoimmune reactions. They exert different functions during the immune response, including presentation of antigens, release of cytokines, cooperation with and activation of T cells, production of auto-antibodies and they may act as regulatory B cells [1]. There is accumulating evidence supporting an active contribution of B cells to different autoimmune diseases, such as systemic lupus erythematosus (SLE), primary Sjögren’s syndrome (pSS) and rheumatoid arthritis (RA) [24]. The importance of B cells in RA has been highlighted by the success of B cell-targeting therapy using the anti-CD20 monoclonal antibody rituximab In parallel to this B cell-specific biologic agent, other anti-B cell therapies are currently under development, especially treatments targeting cytokines implicated in B cell survival and/or differentiation [5]. 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)

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