RITUXIMAB THERAPY IN SYSTEMIC LUPUS ERYTHEMATOSUS - TRANSIENT EFFECTS ON AGE ASSOCIATED B-CELLS

• Immune system’s abnormalities in SLE involve several subsets of the B-cell compartment, including double negative B-cells (DN) and CD11c+CD21- B cells (also referred to as ABC-age associated B cells), which are expanded in the disease. ABC cells are also known to interact with T helper cells, T follicular and peripheral helper cells (1). Rituximab, a chimeric anti- CD20 antibody, depleting B cells, is commonly used off-label as treatment for SLE patients, especially in lupus nephritis. Little is known on the impact of B-cell depletion on such B-cell subsets and on B-T-cell interactions.Objectives:to investigate the effects of rituximab (RTX) on the frequencies of double negative B-cell subsets and CD11c+CD21- ABC cells and as well as T follicular helper (TFH, CXCR5+ PD-1+) and T peripheral helper (TPH, PD-1high) CD4+ T-cell subsets.Methods:15 SLE patients, starting RTX and followed longitudinally up to two years, were analyzed for lymphocyte subsets using multicolor flow cytometry. Cryopreserved PBMC were thawed and stained at the same time together with one buffy coat. Around 1 x 106 PBMC for each panel were labeled and further stained with fluorescent antibodies for B and T-cell markers. For the B-cell panel, PBMC were stained with anti-CD3, CD14, CD16, CD19, IgD, CD27, CD38, CD11c, CD21 and in some samples with anti-CXCR5 antibodies. For the T-cell panel, PBMC were labeled with anti-CD16, CD14, CD19 and CD3, CD4, CD8, PD-1, CCR7, CXCR5, CD45RA antibodies. All patients fulfilled the ACR 1982 classification criteria for SLE. Cellular changes were analyzed in the context of clinical information.Results:in the present cohort, the SLE patients were mainly female (86.6%) and of median age of 36.7 (29.8-49.4) with a disease duration of 6.1(1.6-11.8) years, and active disease with SLEDAI-2K at baseline 12.0 (8.0-16.0). The frequency of age-associated B cells (ABCs; CD27-IgD-CD11c+ CD21-) decreased by 13% (p=0.03) in the first two to four months after rituximab start, while globally the DN (IgD-CD27-) B cells transiently increased by around 3% (p=0.15) at the first follow-up. This increase could not be attributed to the DN1 (CXCR5+CD11c-) or DN2 (CXCR5-CD11c+) subsets but to the CD11c-CXCR5- DN (DN3) B cells (increase= 6.7%, p=0.03). In parallel, T effector cells (CCR7- CD45RA+) and TEMRA (CD45RA+ CCR7-) frequencies increased after first follow up in both CD4+ and CD8+ T cells. The frequency of TFH (CXCR5+ PD-1+) cells did not change after rituximab, however a decrease of PD-1high CD4+ cells was observed in most patients, although not significant, after 2-4 month of treatment. In most patients the frequency of PD-1high CD4+ cells either reduce or stay the same after RTX treatment (reduction= 0.53, p=0.28). After 11-15 months of RTX treatment the frequency of PD-1high CD4+ T cell reduces by a -0.5% in comparison to 2-4 months (p=0.039). The SLEDAI at baseline did not correlate with the frequency of PD-1high CD4+ T cells (r=0.03, p=0.9).Conclusion:the importance of T cell - B cell interactions in SLE pathogenesis was recently strengthened by the identification of the lymphocyte subsets TFH/TPH and ABCs respectively. Here, in the context of rituximab treated SLE, we could detect a reduction in the frequencies of both ABCs and PD-1high T cells after treatment with rituximab, while the DN3 and effector memory T cells frequencies increased. Our data suggests that anti-CD20 mediated B-cell depletion affects both B-cell and T-cell subsets frequencies, and that monitoring these specific cell subsets may be clinically relevant.References:[1]Bocharnikov AV, Keegan J, Wacleche VS, Cao Y, Fonseka CY, Wang G, et al. PD-1hiCXCR5- T peripheral helper cells promote B cell responses in lupus via MAF and IL-21. JCI insight. 2019;4(20)Disclosure of Interests:Francesca Faustini Speakers bureau: More than two years ago and not in relation to any aspect of the present research, Natalie Sippl: None declared, Ragnhild Stålesen: None declared, Karine Chemin: None declared, Iva Gunnarsson: None declared, Vivianne Malmström: None declared.

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