结核分枝杆菌脂糖ManLAM对CE蛋白抗原诱导的B细胞活化的影响

目的甘露糖修饰的脂阿拉伯甘露聚糖(mannose-capped lipoarabinomannan,ManLAM)是结核分枝杆菌细胞壁的主要成分之一,本研究拟探究ManLAM对CE蛋白诱导B细胞抗结核免疫应答的作用及潜在机制。方法磁珠分选活动性肺结核患者B细胞,ManLAM协同CE蛋白离体刺激,CFSE检测增殖,流式检测B细胞凋亡及活化,ELISA检测细胞因子及抗体亚型分泌水平,酶联斑点试验检测B细胞分化抗体分泌细胞的水平。结果ManLAM抑制CE蛋白诱导的B细胞增殖、活化、促炎因子释放和分化为CE蛋白特异性IgG分泌细胞,但对凋亡和分化为IgM分泌细胞无显著影响。ManLAM可通过TLR2抑制CE蛋白特异性IgG1和IgG3的分泌,诱导IgG4的分泌。结论本研究证实ManLAM可抑制B细胞抗结核免疫应答,为结核分枝杆菌免疫逃逸提供了新的理论依据。

Effects of Mycobacterium tuberculosis liposaccharide ManLAM on CE protein-induced B cell activation

Objective To investigate the influence and potential mechanism of mannose-capped lipoarabinomannan(ManLAM)to B cells responding to Mycobacterium tuberculosis(Mtb)infection.Methods B cells were separated from patients with active pulmonary tuberculosis using magnetic beads and then stimulated with ManLAM in combination with CE protein.Flow cytometry was performed to evaluate the apoptosis,proliferation and activation of B cells.The secretion of cytokines and CE protein-specific IgG subclasses were detected by ELISA.ELISPOT assay was used to analyze the influence on the differentiation of B cells into CE protein-specific antibody-secreting cells(ASCs).Results ManLAM inhibited the CE protein-induced proliferation and activation of B cells and the production of pro-inflammatory cytokines,resulting in significantly increased secretion of the immunosuppressive cytokine IL-10.It also inhibited the differentiation of B cells into CE protein-specific IgG secretory cells,but had no significant influence on the differentiation to IgM secretory cells.Moreover,ManLAM inhibited the secretion of CE protein-specific IgG1 and IgG3 and induced the secretion of immunosuppressive IgG4 via TLR2.Conclusions This study suggested that ManLAM could inhibit the anti-tuberculosis immune response of B cells,which provided new theoretical reference for better understanding the immune escape mechanism in Mtb infection.