Mandell Leisa, Moran Anthony P, Cocchiarella Andrew, Houghton JeanMarie, Taylor Nancy, Fox James G, Wang Timothy C, Kurt-Jones Evelyn A
Department of Medicine, University of Massachusetts Medical Center, Worcester 01605, USA.
Infect Immun. 2004 Nov;72(11):6446-54. doi: 10.1128/IAI.72.11.6446-6454.2004.
Molecular and genetic studies have demonstrated that members of the Toll-like receptor (TLR) family are critical innate immune receptors. TLRs are recognition receptors for a diverse group of microbial ligands including bacteria, fungi, and viruses. This study demonstrates that distinct TLRs are responsible for the recognition of Helicobacter lipopolysaccharide (LPS) versus intact Helicobacter bacteria. We show that the cytokine-inducing activity of Helicobacter LPS was mediated by TLR4; i.e., TLR4-deficient macrophages were unresponsive to Helicobacter pylori LPS. Surprisingly, the cytokine response to whole Helicobacter bacteria (H. pylori, H. hepaticus, and H. felis) was mediated not by TLR4 but rather by TLR2. Studies of HEK293 transfectants revealed that expression of human TLR2 was sufficient to confer responsiveness to intact Helicobacter bacteria, but TLR4 transfection was not sufficient. Our studies further suggest that cag pathogenicity island genes may modulate the TLR2 agonist activity of H. pylori as cagA+ bacteria were more active on a per-cell basis compared to cagA mutant bacteria for interleukin-8 (IL-8) cytokine secretion. Consistent with the transfection studies, analysis of knockout mice demonstrated that TLR2 was required for the cytokine response to intact Helicobacter bacteria. Macrophages from both wild-type and TLR4-deficient mice produced a robust cytokine secretion response (IL-6 and MCP-1) when stimulated with intact Helicobacter bacteria. In contrast, macrophages from TLR2-deficient mice were profoundly unresponsive to intact Helicobacter stimulation, failing to secrete cytokines even at high (100:1) bacterium-to-macrophage ratios. Our studies suggest that TLR2 may be the dominant innate immune receptor for recognition of gastrointestinal Helicobacter species.
分子和遗传学研究表明，Toll样受体（TLR）家族成员是关键的天然免疫受体。TLR是多种微生物配体的识别受体，这些配体包括细菌、真菌和病毒。本研究表明，不同的TLR分别负责识别幽门螺杆菌脂多糖（LPS）和完整的幽门螺杆菌。我们发现，幽门螺杆菌LPS的细胞因子诱导活性由TLR4介导；即，TLR4缺陷型巨噬细胞对幽门螺杆菌LPS无反应。令人惊讶的是，对完整幽门螺杆菌（幽门螺杆菌、肝螺杆菌和猫螺杆菌）的细胞因子反应不是由TLR4介导的，而是由TLR2介导的。对HEK293转染细胞的研究表明，人TLR2的表达足以赋予细胞对完整幽门螺杆菌的反应性，但TLR4转染则不足以产生这种反应。我们的研究进一步表明，cag致病岛基因可能调节幽门螺杆菌的TLR2激动剂活性，因为与cagA突变菌相比，cagA+菌在每细胞基础上对白细胞介素-8（IL-8）细胞因子分泌的活性更高。与转染研究一致，对基因敲除小鼠的分析表明，TLR2是对完整幽门螺杆菌产生细胞因子反应所必需的。野生型和TLR4缺陷型小鼠的巨噬细胞在用完整幽门螺杆菌刺激时均产生强烈的细胞因子分泌反应（IL-6和MCP-1）。相比之下，TLR2缺陷型小鼠的巨噬细胞对完整幽门螺杆菌刺激完全无反应，即使在高细菌与巨噬细胞比例（100:1）下也不分泌细胞因子。我们的研究表明，TLR2可能是识别胃肠道幽门螺杆菌的主要天然免疫受体。
