Department of Pulmonary Medicine, Erasmus MC Rotterdam, Rotterdam, the Netherlands.
Department of Rheumatology, Erasmus MC Rotterdam, Rotterdam, the Netherlands.
J Autoimmun. 2024 Feb;143:103168. doi: 10.1016/j.jaut.2024.103168. Epub 2024 Feb 13.
Altered B cell receptor (BCR) signaling has been implicated in the pathogenesis of rheumatoid arthritis (RA). Here we aimed to identify signaling aberrations in autoantibody-positive and autoantibody-negative RA patients by performing a comprehensive analysis of the BCR signaling cascade in different B cell subsets.
We first optimized phosphoflow cytometry for an in-depth analysis of BCR signaling across immunoglobulin isotypes in healthy donors. Subsequently, we compared BCR signaling in circulating B cell subsets from treatment-naïve, newly-diagnosed autoantibody-positive RA and autoantibody-negative RA patients and healthy controls (HCs).
We observed subset-specific phosphorylation patterns of the BCR signalosome in circulating B cells from healthy donors. Compared with HCs, autoantibody-positive RA patients displayed enhanced responses to BCR stimulation for multiple signaling proteins, specifically in naïve and IgA memory B cells. Whereas in unstimulated healthy donor B cells, the phosphorylation status of individual signaling proteins showed only limited correlation, BCR stimulation enhanced the interconnectivity in phosphorylation within the BCR signalosome. However, this strong interconnectivity within the BCR signalosome in stimulated B cells from HCs was lost in RA, especially in autoantibody-positive RA patients. Finally, we observed strong correlations between SYK and BTK protein expression, and IgA and IgG anti-citrullinated protein antibody concentrations in serum from autoantibody-positive RA patients.
Collectively, the isotype-specific analysis of multiple key components of the BCR signalosome identified aberrant BCR signaling responses in treatment-naïve autoantibody-positive RA patients, particularly in naïve B cells and IgA memory B cells. Our findings support differential involvement of dysregulated BCR signaling in the pathogenesis of autoantibody-positive and autoantibody-negative RA.
B 细胞受体（BCR）信号的改变与类风湿关节炎（RA）的发病机制有关。在此，我们旨在通过对不同 B 细胞亚群的 BCR 信号级联进行全面分析，来鉴定自身抗体阳性和自身抗体阴性 RA 患者中的信号异常。
我们首先优化了磷酸化流式细胞术，以深入分析健康供者中免疫球蛋白同种型的 BCR 信号。随后，我们比较了治疗初发、新诊断的自身抗体阳性 RA 和自身抗体阴性 RA 患者及健康对照者（HCs）循环 B 细胞亚群中的 BCR 信号。
我们观察到健康供者循环 B 细胞中 BCR 信号转导体的亚群特异性磷酸化模式。与 HCs 相比，自身抗体阳性 RA 患者的多个信号蛋白对 BCR 刺激的反应增强，尤其是在幼稚和 IgA 记忆 B 细胞中。而在未刺激的健康供者 B 细胞中，单个信号蛋白的磷酸化状态仅显示出有限的相关性，BCR 刺激增强了 BCR 信号转导体中的磷酸化的相互连接。然而，这种在 HCs 刺激的 B 细胞中 BCR 信号转导体的强相互连接在 RA 中丢失了，尤其是在自身抗体阳性 RA 患者中。最后，我们观察到自身抗体阳性 RA 患者血清中 SYK 和 BTK 蛋白表达以及 IgA 和 IgG 抗瓜氨酸化蛋白抗体浓度之间存在强烈相关性。
综上所述，对 BCR 信号转导体的多个关键成分的同种型特异性分析，鉴定出治疗初发的自身抗体阳性 RA 患者中存在异常的 BCR 信号反应，尤其是在幼稚 B 细胞和 IgA 记忆 B 细胞中。我们的研究结果支持失调的 BCR 信号在自身抗体阳性和自身抗体阴性 RA 的发病机制中存在差异作用。
