脂多糖持续刺激巨噬细胞的免疫学机制初探

目的:探讨巨噬细胞在脂多糖(LPS)的持续刺激下产生免疫抑制后的表型变化及对T细胞影响的分子机制。方法:蔗糖密度梯度离心法从全血中分离人外周血单个核细胞,结合磁珠细胞分选技术分选出单核细胞,体外诱导单核细胞分化为巨噬细胞,以未处理和IFN-γ处理为对照,对LPS处理48 h的巨噬细胞进行形态学观察、细胞表面分子(HLA-DR、CD14、CCR7、HLA-ABC及CD40)表达的检测和细胞因子(IL-10、IL-12、IL-6及TNF-α)分泌水平的检测。同时将LPS诱导的巨噬细胞与CD3+T细胞进行异体共培养,进一步观察巨噬细胞对T细胞增殖能力的影响。用实时荧光定量PCR验证Toll样受体4(TLR4)信号通路中的非My D88依赖型途径相关分子的表达水平。结果:LPS处理48 h的巨噬细胞,抗原递呈能力(HLA-DR)下降,免疫抑制细胞因子IL-10升高,把LPS诱导的巨噬细胞与异体T细胞共培养6 d,其促进CD8+T细胞增殖的能力较弱。实时荧光定量PCR结果显示LPS持续刺激下巨噬细胞的TRIF、IRF3和CIITA均呈下调状态。结论:持续LPS处理巨噬细胞48 h后,巨噬细胞呈现一种免疫抑制的状态,且其刺激CD8+T细胞增殖的能力减弱,这种状态与非My D88依赖型TLR4信号通路受损有关。

Immunological mechanism of long-term stimulation by LPS in macrophages

AIM: To investigate the molecular mechanism and the immunosuppressive phenotype of macrophages under long-term exposure to lipopolysaccharide (LPS). METHODS: We used Ficoll-Hypaque density gradient centri-fugation combined with MicroBeads Separation Kits to separate peripheral blood mononuclear cells from human blood, and then induced the monocytes into macrophages. We observed the morphology of the macrophages by treating the cells with LPS for 48 h, in comparison with a negative control and IFN-γ treatment. ELISA was used to detect the levels of cytokines, such as IL-10, IL-12, IL-6 and TNF-α, and flow cytometry was used to detect the expression of the surface molecules (HLA-DR, CD14, CCR7, HLA-ABC and CD40). To observe the effect of macrophage on T cell proliferation, co-culture experiment was carried out for 6 d. Real-time PCR was used to validate the expression levels of molecules related to MyD88-independent pathway in Toll-like receptor 4 (TLR4) signal pathway. RESULTS: The antigen-presenting ability of the macrophages was reduced and the IL-10 expression level was increased after the cells were treated with LPS for 48 h. We observed a poor proliferative capacity of CD8⁺ T cells after co-culturing of LPS-induced macrophages with CD3⁺ T cells for 6 d. The results of real-time PCR indicated that TRIF, IRF3 and CIITA were down-regulated in LPS-induced macrophages.CONCLUSION: We successfully established a macrophage model in vitro and observed that LPS-induced macrophages into an immunosuppressive phenotype with poor CD8⁺ T cell proliferative capacity, in which MyD88-independent TLR4 signaling pathway was impaired.