FcγRⅡB1介导的信号传导异常与SLE患者B细胞的过度活化

目的:观察系统性红斑狼疮(SLE)患者B细胞表面功能分子表达的特征及其功能状态,评价以FcγRⅡB1(CD32)为代表的B细胞自身抑制调节机制在SLE发病中的作用。方法:采用Ficoll密度梯度离心法分离出人外周血单个核细胞(PBMC),并以免疫磁珠法(MACS)分离纯化B细胞。采用荧光分光光度法检测B细胞受不同激活物刺激后细胞内钙(Ca2 ]i)的反应。用ELISA法检测B细胞与刺激物共同培养后所分泌IgG的量。采用流式细胞术及间接免疫荧光染色法,检测B细胞膜表面CD32、CD19及IgM的表达水平。结果:(1)以羊抗人μ链的F(ab′)2片段及完整IgG分别刺激SLE患者B细胞时,其Ca2 ]i反应的比值显著低于类风湿性关节炎(RA)患者(P<0.05)及正常人对照(P<0.01)。(2)分别用葡萄球菌A蛋白(SPA)单独刺激与SPA和羊抗人μ链的完整IgG抗体共同刺激SLE患者的B细胞所分泌的IgG的比值,明显低于RA患者及正常人对照组(P<0.05)。(3)SLE患者与RA患者及正常对照组B细胞上CD19、CD32及IgM的表达无统计学意义(P>0.05)。结论:SLE患者B细胞上CD32抑制性信号传导的异常,可能是导致B细胞过度活化的重要机制。

The abnormality of FcγRⅡB1-mediated signaling and the hyperactivity of B cells from patients with systemic lupus erythematosus

AIM: To evaluate the effect of FcgammaRIIB(1) (CD32) representative self-inhibitory adjustive mechanism of B cells on pathogenesis of systemic lupus erythematosus (SLE) by observing the expression characteristic and functional state of molecules on the surface of B cells from SLE patients. METHODS: The peripheral blood mononuclear cells (PBMC) were prepared by density gradient centrifugation, and the B cells were isolated from PBMC by magnetic activated cell sorting (MACS). The fluxes of intracytoplasmic calcium (Ca(2+)](i)) of B cells activated by different activators were measured by fluorescence spectrophotometric method. The IgG production by B cells cultured with activators was assayed by ELISA. The expression levels of CD32, CD19, and IgM on the surface of B cells were measured by flow cytometry. RESULTS: (1)After B cells were stimulated with goat anti-human mu chain F(ab')(2) fragments and whole IgG respectively, the ratio of Ca(2+)](i) response by F(ab')(2) fragments to whole IgG was significantly lower in SLE B cells compared to rheumatoid arthritis (RA)(P<0.05) or normal (P<0.01) B cells. (2)The ratio of total IgG production by B cells cultured with staphylococcal protein A (SPA) to SPA plus IgG anti-mu chain was significantly lower in SLE patients compared to RA patients or normal individuals (P<0.05). (3)There was no obvious difference in the expression of CD19, CD32, and IgM on the surface of B cells from SLE, RA patients and normal individuals (P>0.05). CONCLUSION: The inhibitory signaling abnormality of CD32 possibly contributes to the mechanism of hyperactivity of human SLE B cells.