Background/Purpose:

Recently, a specific and functionally important subset of regulatory B cells (B_reg) that negatively regulate autoimmunity and inflammation has been described. B_reg cells exert their suppressive role through the production of interleukin-10 (IL-10), and can be immunophenotypically identified by high expression of CD38 and CD24.  Possible involvement of B_reg cells in primary Sjögren’s syndrome (pSS) has not been yet elucidated.  This study aimed to assess the frequency and number of B_reg cells in pSS-patients, the impact of rituximab (RTX) treatment on B_reg cell reconstitution, and the association between B_reg cells and pSS disease activity score.

Methods:

Peripheral blood mononuclear cells (PBMCs) were isolated from 12 pSS-patients (at baseline and 48 weeks after RTX-treatment) and from 8 age- and sex-matched healthy controls (HC). Frequency and number of circulating CD38^highCD24^highCD19⁺ B_reg cells were assessed by flow cytometry. Next, since IL-10 secretion was recognized as a functional mechanism of suppression in B_reg cells, we determined the frequency and number of IL-10 producing B-cells after in vitro stimulation of PBMCs with CpG (0.5mg/ml) for 3 days and re-stimulation with PMA (5ng/ml) and Ca-I (0,2mg/ml) in the presence of Brefeldin A (10mg/ml) during the last 16 hours. Expression of TNFα was used to discriminate between B_reg cells (IL-10⁺ TNFα^–) and TNFα⁺ effector B cells (IL-10^– TNFα⁺; B_eff). Intracellular production of IL-10 and TNFα in B cells were determined by flow cytometry. In addition, EULAR Sjögren Syndrome Disease Activity scores (ESSDAI) were calculated for each patient before and after RTX-treatment, and compared to the B_reg results in order to assess the clinical relevance of data.

Results:

At baseline, based on the surface phenotype of B_reg cells (CD38^highCD24^highCD19⁺), pSS-patients displayed higher frequencies and numbers of B_reg cells in blood compared to HCs. Following RTX-treatment, a significant increase in CD38^highCD24^highCD19⁺ B_reg cell frequencies and numbers was observed in pSS-patients when compared to baseline and HCs. Since IL-10 production is the hallmark of B_reg cells, we also measured IL-10 production by B-cells. Frequencies and numbers of IL-10 producing B_reg cells (IL-10⁺ TNFα^–) did, however, not differ between pSS-patients before and after RTX-treatment and HCs. Ratios of B_reg:B_eff did not significantly change after RTX-treatment too. Frequencies and numbers of both IL-10⁺TNFα^– B_reg cells as well as CD38^highCD24^highCD19⁺ B_reg cells at baseline correlated negatively with ESSDAI.

Conclusion:

Frequencies and numbers of IL-10 producing B_reg cells were not impaired in pSS-patients, neither before nor after RTX-treatment. Given that circulating IL-10 producing B_reg cells correlate negatively with ESSDAI, these B_Reg cells might serve as a monitor to assess disease activity in pSS-patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/frequencies-and-numbers-of-circulating-il-10-producing-regulatory-b-cells-are-not-disturbed-in-pss-patients-but-correlate-negatively-with-the-eular-sjogren-syndrome-disease-activity-score-essdai/