Possible involvement of M. bovis BCG-producing TLR2 ligand to generate protective immunity by inducing TH1 cytokine productions

在感染早期产生的各种炎症介质中，TH 1细胞因子如干扰素-γ、白细胞介素12（IL-12）和IL-18对保护性T细胞的发育起关键作用。还已知这些细胞因子的产生是由活的但不是被杀死的细菌诱导的，所述细菌能够产生保护性免疫。为了鉴定有助于TH 1细胞因子产生的分枝杆菌因子，我们从活BCG（vBCG）的1d培养物制备培养物滤液并测量烟碱诱导活性。培养物滤液引起腹膜巨噬细胞产生IL-12 p40。而灭活卡介苗制备的类似制剂不能诱导细胞因子的产生。在C3 H/HeJ小鼠巨噬细胞中检测到了该化合物的精氨酸诱导活性，且不受LPS拮抗剂E5531的影响。此外，培养滤液在用TLR 4和MD-2转染的HEK 293细胞中不诱导NF-κB活化。然而，通过用vBCG衍生的培养滤液刺激，在用TLR 2转染的细胞中诱导转录因子的激活。的干扰素诱导活性是耐用DNA酶处理和部分敏感的处理与蛋白酶K，这表明一些蛋白质和非蛋白质的因素参与细胞因子的生产。在从活的但未杀死的M获得的培养滤液中也检测到类似的活性。结核病H37 Rv.这些结果表明，活分枝杆菌的早期分泌组分通过TLR 2依赖性途径激活巨噬细胞产生IL-12。这可能是细菌和巨噬细胞之间产生保护性免疫的关键相互作用。

Among various inflammatory mediators produced at the early stage of infection, TH1 cytokines such as interferon-γ, interleukin 12 (IL-12) and IL-18 play a pivotal role for development of protective T cells. It is further known that the production of these cytokines is induced by viable, but not killed bacteria, which are capable of generating protective immunity. To identify the mycobacterial factor contributing to the TH1 cytokine productions, we prepared a culture filtrate from 1d-culture of viable BCG (vBCG) and measured the cytokine-inducing activity. The culture filtrate elicited IL-12p40 production from peritoneal macrophages. However, the similar preparation derived from killed BCG did not induce the cytokine production. The cytokine-inducing activity was detected in macrophages of C3H/HeJ mice and was not affected by E5531, LPS antagonist. Furthermore, the culture filtrate did not induce NF-κB activation in HEK293 cells transfected with TLR4 and MD-2. However, activation of the transcription factor was induced in cells transfected with TLR2 by stimulation with vBCG-derived culture filtrate. The cytokine-inducing activity was resistant to treatment with DNase and partially sensitive to treatment with proteinase K, suggesting that some proteinaceous and non-proteinaceous factors are involved in the cytokine production. The similar activity was also detected in the culture filtrate obtained from viable, but not killed M. tuberculosis H37Rv. These results suggest that the early secreted components from viable mycobacteria activate macrophages to produce IL-12 via TLR2 dependent pathway. It is likely that this is a critical interaction between bacteria and macrophages for the generation of protective immunity.