Immunomodulation Research Group, School of Biotechnology, Dublin City University, Ireland.
PLoS Pathog. 2011 Jun;7(6):e1002076. doi: 10.1371/journal.ppat.1002076. Epub 2011 Jun 30.
Clostridium difficile is the etiological agent of antibiotic-associated diarrhoea (AAD) and pseudomembranous colitis in humans. The role of the surface layer proteins (SLPs) in this disease has not yet been fully explored. The aim of this study was to investigate a role for SLPs in the recognition of C. difficile and the subsequent activation of the immune system. Bone marrow derived dendritic cells (DCs) exposed to SLPs were assessed for production of inflammatory cytokines, expression of cell surface markers and their ability to generate T helper (Th) cell responses. DCs isolated from C3H/HeN and C3H/HeJ mice were used in order to examine whether SLPs are recognised by TLR4. The role of TLR4 in infection was examined in TLR4-deficient mice. SLPs induced maturation of DCs characterised by production of IL-12, TNFα and IL-10 and expression of MHC class II, CD40, CD80 and CD86. Furthermore, SLP-activated DCs generated Th cells producing IFNγ and IL-17. SLPs were unable to activate DCs isolated from TLR4-mutant C3H/HeJ mice and failed to induce a subsequent Th cell response. TLR4⁻/⁻ and Myd88⁻/⁻, but not TRIF⁻/⁻ mice were more susceptible than wild-type mice to C. difficile infection. Furthermore, SLPs activated NFκB, but not IRF3, downstream of TLR4. Our results indicate that SLPs isolated from C. difficile can activate innate and adaptive immunity and that these effects are mediated by TLR4, with TLR4 having a functional role in experimental C. difficile infection. This suggests an important role for SLPs in the recognition of C. difficile by the immune system.
艰难梭菌是人类抗生素相关性腹泻（AAD）和伪膜性结肠炎的病原体。表面层蛋白（SLP）在这种疾病中的作用尚未得到充分探索。本研究旨在探讨 SLP 在艰难梭菌识别和随后激活免疫系统中的作用。评估了骨髓来源树突状细胞（DC）暴露于 SLP 后产生炎症细胞因子、表达细胞表面标志物及其产生辅助性 T 细胞（Th）反应的能力。使用 C3H/HeN 和 C3H/HeJ 小鼠分离的 DC 来检查 SLP 是否被 TLR4 识别。在 TLR4 缺陷小鼠中检查 TLR4 在感染中的作用。SLP 诱导 DC 成熟，其特征是产生 IL-12、TNFα 和 IL-10 以及 MHC Ⅱ类、CD40、CD80 和 CD86 的表达。此外，SLP 激活的 DC 产生 IFNγ 和 IL-17 的 Th 细胞。SLP 无法激活来自 TLR4 突变型 C3H/HeJ 小鼠的 DC，也无法诱导随后的 Th 细胞反应。TLR4⁻/⁻和 Myd88⁻/⁻，但不是 TRIF⁻/⁻小鼠比野生型小鼠更容易感染艰难梭菌。此外，SLP 在 TLR4 下游激活 NFκB，但不激活 IRF3。我们的结果表明，从艰难梭菌分离的 SLP 可以激活先天和适应性免疫，并且这些作用是由 TLR4 介导的，TLR4 在实验性艰难梭菌感染中具有功能作用。这表明 SLP 在免疫系统识别艰难梭菌方面具有重要作用。
