肺炎支原体感染患儿TLR4/NF-κB介导机体细胞免疫及体液免疫应答的作用

Role of TLR4/NF-κB pathway in mediating cellular and humoral immune responses in children with Mycoplasma pneumoniae infection

目的分析肺炎支原体感染患儿炎症因子、T淋巴细胞表达水平变化,并探讨Toll样受体4(TLR4)/核因子κB(NF-κB)途径在机体细胞免疫及体液免疫应答中的作用机制。方法选取2021年1月-2022年12月西南医科大学附属医院收治的肺炎支原体感染患儿120例设为感染组,并以同期105名健康体检的健康儿童作为对照组;采用聚合酶链式反应(PCR)检测两组研究对象外周血中TLR4、NF-κB、抑制蛋白κB(IκB)mRNA相对表达量,并比较两组血清中白细胞介素-6(IL-6)、IL-8、肿瘤坏死因子-α(TNF-α);采用流式细胞仪检测CD_(3)^(+)、CD_(4)^(+)及CD_(4)^(+)/CD_(8)^(+)及CD_(4)^(+)CD_(25)^(+)调节性T细胞(Treg)水平。结果感染组患儿IL-6、IL-8、TNF-α高于对照组,感染组患儿TLR4 mRNA、NF-κB mRNA相对表达量高于对照组,IκB mRNA低于对照组(P<0.05);感染组患儿外周CD_(4)^(+)CD_(25)^(+)Treg、CD_(8)^(+)高于对照组,CD_(3)^(+)、CD_(4)^(+)以及CD_(4)^(+)/CD_(8)^(+)低于对照组(P<0.05);MP感染患儿TLR4、NF-κB与IL-6、IL-8和TNF-α均呈正相关(P<0.05),IκB与IL-6、IL-8和TNF-α均呈负相关(P<0.05);TLR4、NF-κB与CD_(3)^(+)、CD_(4)^(+)均呈负相关,而与CD_(8)^(+)、CD_(4)^(+)CD_(25)^(+)Treg均呈正相关;IκB与CD_(3)^(+)、CD_(4)^(+)均呈正相关,而与CD_(8)^(+)、CD_(4)^(+)CD_(25)^(+)Treg均呈负相关(P<0.05)。结论肺炎支原体感染可激活TLR4/NF-κB信号通路,该通路介导机体细胞免疫和体液免疫应答,导致淋巴细胞亚群失调,同时可促进多种炎性因子IL-6、IL-8、TNF-α释放,诱发肺部炎症反应。

OBJECTIVE To analyze the changes in the expression levels of inflammatory factors and T lymphocyte in children with Mycoplasma pneumoniae(MP)infection and to investigate the mechanism of the Toll-like receptor 4(TLR4)/Nuclear Factor-κB(NF-κB)pathway in cellular and humoral immune responses.METHODS A total of 120 children with MP infection admitted to the affiliated hospital of Southwest Medical University from Jan.2021 to Dec.2022 were selected as the infection group,and 105 healthy children who underwent physical examination during the same period were selected as the control group.The relative expression levels of TLR4,NF-κB,and inhibitor ofκB(IκB)mRNA in peripheral blood of the two groups of study subjects were detected using polymerase chain reaction(PCR)method,and the levels of interleukin-6(IL-6),IL-8,and tumor necrosis factor-α(TNF-α)in serum were compared between the two groups.Flow cytometry was used to detect the levels of CD_(3)^(+),CD_(4)^(+),CD_(4)^(+)/CD_(8)^(+),and CD_(4)^(+)CD_(25)^(+)regulatory T cells(Tregs).RESULTS The levels of IL-6,IL-8,and TNF-αwere higher in the infection group than control group.The relative expression levels of TLR4 and NF-κB mRNA in the infection group were higher than the control group,while IκB mRNA was lower than the control group(P<0.05).The peripheral CD_(4)^(+)CD_(25)^(+)Tregs and CD_(8)^(+)levels were higher in the infection group than in the control group,while CD_(3)^(+),CD_(4)^(+),and CD_(4)^(+)/CD_(8)^(+)levels were lower than the control group(P<0.05).The TLR4 and NF-κB in children with MP infection were positively correlated with IL-6,IL-8,and TNF-α(P<0.05),while the expression level of IκB was negatively correlated with the IL-6,IL-8,and TNF-α(P<0.05).TLR4 and NF-κB expression levels were negatively correlated with CD_(3)^(+)and CD_(4)^(+),and positively correlated with CD_(8)^(+)and CD_(4)^(+)CD_(25)^(+)Treg levels,while IκB expression level was positively correlated with CD_(3)^(+)and CD_(4)^(+),and negatively correlated with CD_(8)^(+)and CD_(4)^(+)CD_(25)^(+)Treg levels(P<0.05).CONCLUSION Mycoplasma pneumoniae infection activated the TLR4/NF-κB signaling pathway,which mediated the cellular and humoral immune responses,leading to the dysfunction of lymphocyte subpopulations,as well as promoting the release of variety of inflammatory factors such as IL-6,IL-8,and TNF-α,and inducing pulmonary inflammatory response.