Kim Woo Sik, Yoon Joo-Heon, Shin Min-Kyoung, Shin Sung Jae
Department of Microbiology and Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea.
Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup, South Korea.
Front Microbiol. 2019 Aug 7;10:1795. doi: 10.3389/fmicb.2019.01795. eCollection 2019.
subspecies (MAH) is the most common agent causing nontuberculous mycobacterial disease in humans. It mainly causes chronic and slowly progressive pulmonary disease (PD), which requires a long-term treatment and allows opportunistic co-infection by common pulmonary pathogens such as , , and spp., thereby resulting in alteration of host immune response. In the present study, we investigated the phenotypical and functional alterations of dendritic cells (DCs), a bridge antigen-presenting cell between innate and adaptive immunity, following MAH infection in response to various toll-like receptor (TLR) agonists mimicking co-infection conditions, along with subsequent T cell response. Interestingly, MAH-infected DCs produced interleukin (IL)-10 significantly and decreased the level of IL-12p70 in response to Poly I:C and LPS, although not so in response to Pam3CSK4, imiquimod, or CpG oligodeoxynucleotide, thereby indicating that the TLR3 and TLR4 agonists functionally altered MAH-infected DCs toward a tolerogenic phenotype. Moreover, IL-10-producing tolerogenic DCs were remarkably induced by MAH and co-infection. To precisely elucidate how these TLR agonists induce tolerogenic DCs upon MAH infection, we sought to clarify the major mechanisms involved, using LPS, which caused the greatest increase in IL-10 production by the TLR agonists. Increased IL-10 stimulated the creation of tolerogenic DCs by significantly reducing MHC class II expression and MHC class II-antigen presentation, eventually inhibiting CD4 T cell proliferation, along with decreased IFN-γ and IL-2. The tolerogenic phenotypes of MAH/LPS-treated DCs were restored by anti-IL-10 neutralization, validating the induction of tolerogenicity by IL-10. Interestingly, IL-10-producing-tolerogenic DCs were observed after infection with live MAH, rather than with inactivated or dead MAH. In addition, TLR2 and TLR4 DCs confirmed the association of IL-10 production with TLR2 and TLR4 signaling; IL-10 production synergistically increased when both TLR4 and TLR2 were involved. Expression of Cox2 and PGE2 increased along with IL-10 while that of IL-10 was inhibited by their selective inhibitors celecoxib and anti-EP2 antibody, respectively. Thus, the tolerogenic phenotypes of MAH/LPS-treated DCs were proven to be induced by Cox-2/PGE2-dependent EP2 signaling as the main mechanism. These findings may provide important clues that the tolerogenic cascade in MAH-infected DCs induced by TLR 4 signaling can alter host immune response.
亚种（MAH）是人类非结核分枝杆菌病最常见的病原体。它主要引起慢性和缓慢进展性肺部疾病（PD），这种疾病需要长期治疗，并且会使宿主易受常见肺部病原体如、和 spp. 的机会性共感染，从而导致宿主免疫反应改变。在本研究中，我们研究了树突状细胞（DCs）的表型和功能变化，DCs 是先天性免疫和适应性免疫之间的桥梁抗原呈递细胞，在 MAH 感染后，针对模拟共感染条件的各种 Toll 样受体（TLR）激动剂以及随后的 T 细胞反应进行了研究。有趣的是，MAH 感染的 DCs 在对 Poly I:C 和 LPS 作出反应时显著产生白细胞介素（IL）-10，并降低了 IL-12p70 的水平，尽管对 Pam3CSK4、咪喹莫特或 CpG 寡脱氧核苷酸没有这种反应，这表明 TLR3 和 TLR4 激动剂在功能上使 MAH 感染的 DCs 向耐受性表型转变。此外，MAH 和共感染显著诱导了产生 IL-10 的耐受性 DCs。为了精确阐明这些 TLR 激动剂在 MAH 感染时如何诱导耐受性 DCs，我们试图使用 LPS 来阐明其中涉及的主要机制，LPS 能使 TLR 激动剂诱导的 IL-10 产生增加最多。IL-10 的增加通过显著降低 MHC II 类分子表达和 MHC II 类分子-抗原呈递来刺激耐受性 DCs 的产生，最终抑制 CD4 T 细胞增殖，同时降低 IFN-γ 和 IL-2。通过抗 IL-10 中和恢复了 MAH/LPS 处理的 DCs 的耐受性表型，验证了 IL-10 诱导耐受性。有趣的是，在感染活的 MAH 后观察到了产生 IL-10 的耐受性 DCs，而不是灭活或死亡的 MAH。此外，TLR2 和 TLR4 DCs 证实了 IL-10 产生与 TLR2 和 TLR4 信号传导之间的关联；当 TLR4 和 TLR2 都参与时，IL-10 产生协同增加。Cox2 和 PGE2 的表达随着 IL-10 增加，而 IL-10 的表达分别被它们的选择性抑制剂塞来昔布和抗 EP2 抗体抑制。因此，MAH/LPS 处理的 DCs 的耐受性表型被证明是由 Cox-2/PGE2 依赖性 EP2 信号传导作为主要机制诱导的。这些发现可能提供重要线索，即 TLR 4 信号传导诱导的 MAH 感染的 DCs 中的耐受性级联反应可以改变宿主免疫反应。
