Assi Lakhvir K, Wong See Heng, Ludwig Andreas, Raza Karim, Gordon Caroline, Salmon Michael, Lord Janet M, Scheel-Toellner Dagmar
Institute of Biomedical Research, University of Birmingham, Birmingham, UK.
Arthritis Rheum. 2007 Jun;56(6):1776-86. doi: 10.1002/art.22697.
The tumor necrosis factor (TNF) family member B lymphocyte stimulator (BLyS) is an important regulator of B cell-dependent autoimmunity. Similar to other TNF family members, it is generally expressed as a transmembrane protein and cleaved from the surface to release its active soluble form. This study was undertaken to investigate the expression of BLyS and regulation of BLyS release from the surface of neutrophils infiltrating the rheumatoid joint.
BLyS expression was studied in neutrophils from the synovial fluid and peripheral blood of patients with rheumatoid arthritis (RA) and healthy controls, by flow cytometry, Western blotting, and immunofluorescence analyses. Peripheral blood neutrophils cultured with 50% RA synovial fluid were study for membrane expression of BLyS. Neutrophils were exposed to a range of proinflammatory cytokines to study the mechanisms of surface loss of BLyS.
Expression of BLyS was detected on the surface of peripheral blood neutrophils from both RA patients and healthy controls, whereas BLyS expression on synovial fluid neutrophils was very low. Constitutive expression of BLyS was observed in neutrophils, both on the cell membrane and in intracellular stores; however, BLyS release from each of these sites was found to be regulated independently. Of the various cytokine stimuli, only TNFalpha triggered release of BLyS from the neutrophil membrane. This process led to release of physiologically relevant quantities of soluble BLyS, which was dependent on the presence of the pro-protein convertase furin. In contrast, stimulation of neutrophils with granulocyte colony-stimulating factor induced BLyS release from the intracellular stores. Incubation of peripheral blood neutrophils with RA synovial fluid led to TNFalpha-dependent shedding of BLyS from the cell surface.
These findings indicate that as neutrophils enter the site of inflammation, they release surface-expressed BLyS in a TNFalpha-dependent manner, and thus may contribute to local stimulation of autoimmune B cell responses.
肿瘤坏死因子（TNF）家族成员B淋巴细胞刺激因子（BLyS）是B细胞依赖性自身免疫的重要调节因子。与其他TNF家族成员相似，它通常以跨膜蛋白形式表达，并从表面裂解以释放其活性可溶性形式。本研究旨在调查类风湿关节中浸润的中性粒细胞表面BLyS的表达及BLyS释放的调节。
通过流式细胞术、蛋白质印迹法和免疫荧光分析，研究类风湿关节炎（RA）患者和健康对照者滑膜液和外周血中性粒细胞中BLyS的表达。用50% RA滑膜液培养外周血中性粒细胞，研究BLyS的膜表达。将中性粒细胞暴露于一系列促炎细胞因子，以研究BLyS表面丢失的机制。
在RA患者和健康对照者的外周血中性粒细胞表面均检测到BLyS的表达，而滑膜液中性粒细胞上的BLyS表达非常低。在中性粒细胞的细胞膜和细胞内储存中均观察到BLyS的组成性表达；然而，发现从这些部位释放的BLyS是独立调节的。在各种细胞因子刺激中，只有肿瘤坏死因子α（TNFα）触发中性粒细胞膜上BLyS的释放。这个过程导致释放生理相关量的可溶性BLyS，这依赖于前体蛋白转化酶弗林蛋白酶的存在。相反，用粒细胞集落刺激因子刺激中性粒细胞可诱导BLyS从细胞内储存中释放。用RA滑膜液孵育外周血中性粒细胞导致细胞表面TNFα依赖性的BLyS脱落。
这些发现表明，当中性粒细胞进入炎症部位时，它们以TNFα依赖性方式释放表面表达的BLyS，因此可能有助于局部刺激自身免疫性B细胞反应。
