A BAFF/APRIL-dependent TLR3-stimulated pathway enhances the capacity of rheumatoid synovial fibroblasts to induce AID expression and Ig class-switching in B cells
A BAFF/APRIL-dependent TLR3-stimulated pathway enhances the capacity of rheumatoid synovial fibroblasts to induce AID expression and Ig class-switching in B cells
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DOI：
10.1136/ard.2011.150219
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发表时间：
2011-10-01
影响因子：
27.4
通讯作者：
Pitzalis, Costantino
中科院分区：
文献类型：
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作者：
Bombardieri, Michele;Kam, Ngar-Woon;Pitzalis, Costantino
目的探讨类风湿关节炎滑膜成纤维细胞（RASF）与B细胞相互作用中Toll样受体（TLR）信号通路和B细胞存活/增殖因子的作用。分析类风湿性关节炎皮肤成纤维细胞（RADF）和骨关节炎滑膜成纤维细胞（OASF）在静息条件下和在用TLR 2/TLR 3/TLR 4刺激后B细胞存活/增殖因子BAFF和APRIL的表达。TLR 4配体。将未转换的IgD+B细胞与RASF/OASF/RADF在存在/不存在TLR配体和存在/不存在BAFF/APRIL阻断抗体的情况下共培养。激活诱导的胞苷脱氨酶（AID）mRNA的表达，I γ-C μ和I α-C μ的环状转录本（CT的标志物正在进行的类转换IgG和伊加）和IgM/A/G生产进行了测量，以评估功能激活的B cells.Results TLR 3和TLR 4在较小程度上，但不是TLR 2刺激，诱导高达类似的1000倍BAFF mRNA和增加可溶性BAFF释放。APRIL受TLR 3的调节不太显著。与RADF相比，静息和TLR 3刺激的RASF释放更高水平的BAFF/APRIL。在与B细胞共培养中，TLR 3刺激RASF而不是RADF强烈增强AID表达、I γ-C μ和I α-C μ CT以及向IgG/伊加的类别转换。阻断BAFF/APRIL信号通路可完全抑制TLR 3诱导的RASF依赖的AID、CTs的表达和IgG/伊加的分泌。结论RASF在TLR 3刺激下产生高水平的BAFF和APRIL。这些因子在IgD+ B细胞中直接调节AID表达、类别转换重组和IgG/伊加产生中是关键的。总之，这项工作突出了一个新的和基本的作用，TLR 3/B细胞存活因子轴在维持类风湿关节炎滑膜中的B细胞活化。
Objectives To dissect the role of toll-like receptor (TLR) signalling and B cell survival/proliferating factors in the crosstalk between rheumatoid arthritis synovial fibroblasts (RASF) and B cells.Methods RASF, rheumatoid arthritis dermal fibroblasts (RADF) and osteoarthritis synovial fibroblasts (OASF) were analysed for the expression of B cell survival/proliferating factors BAFF and APRIL in resting conditions and upon stimulation with TLR2/TLR3/TLR4 ligands. Unswitched IgD+B cells were co-cultured with RASF/OASF/RADF in the presence/absence of TLR ligands and with/without BAFF/APRIL blocking antibodies. Activation-induced cytidine deaminase (AID) mRNA expression, I gamma-C mu and I alpha-C mu circular transcripts (CTs; markers of ongoing class-switching to IgG and IgA) and IgM/A/G production were measured to assess functional activation of B cells.Results TLR3 and to a lesser extent TLR4, but not TLR2 stimulation, induced up to similar to 1000-fold BAFF mRNA and increased soluble BAFF release. APRIL was less significantly regulated by TLR3. Resting and TLR3-stimulated RASF released higher levels of BAFF/APRIL compared with RADF. TLR3 stimulation of RASF but not RADF in co-culture with B cells strongly enhanced AID expression, I gamma-C mu and I alpha-C mu CTs and class-switching to IgG/IgA. Blockade of BAFF/APRIL signalling completely inhibited TLR3-induced, RASF-dependent expression of AID, CTs and the secretion of IgG/IgA.Conclusions RASF produce high levels of BAFF and APRIL constitutively and in response to TLR3 stimulation. These factors are critical in directly modulating AID expression, class-switch recombination and IgG/IgA production in IgD+ B cells. Overall, this work highlights a novel and fundamental role for the TLR3/B cell survival factor axis in sustaining B cell activation in the rheumatoid arthritis synovium.