Konishi Masanori, Nishitani Chiaki, Mitsuzawa Hiroaki, Shimizu Takeyuki, Sano Hitomi, Harimaya Atsushi, Fujii Nobuhiro, Himi Tetsuo, Kuroki Yoshio
Department of Biochemistry, Sapporo Medical University School of Medicine, Japan.
Eur J Immunol. 2006 Jun;36(6):1527-36. doi: 10.1002/eji.200535542.
Alloiococcus otitidis has been found to be associated with otitis media with effusion. In this study we investigated whether TLR2 and collectins, surfactant protein A (SP-A) and mannose-binding lectin (MBL), interacted with A. otitidis. Both SP-A and MBL bound to A. otitidis in a Ca(2+)-dependent manner. A. otitidis induced IL-8 secretion from U937 cells and NF-kappaB activation in TLR2-transfected HEK293 cells. However, the cells transfected with the mutant TLR2(P681H) did not respond to A. otitidis. In addition, A. otitidis co-sedimented a recombinant soluble form of the extracellular TLR2 domain, indicating direct binding of the bacterium to TLR2. SP-A and MBL augmented the phagocytosis of A. otitidis by J774A.1 cells. The collectin-stimulated phagocytosis of A. otitidis was significantly attenuated when fucoidan and polyinosinic acid were co-incubated. Immunoblotting analysis revealed that MBL was present in the middle ear effusion from patients with otitis media. These results demonstrate that A. otitidis is a ligand for the collectins and TLR2, and that the collectins enhance the phagocytosis of A. otitidis by macrophages, suggesting important roles of the collectins and TLR2 in the innate immunity of the middle ear against A. otitidis infection.
已发现耳道球菌与分泌性中耳炎有关。在本研究中，我们调查了Toll样受体2（TLR2）和凝集素、表面活性蛋白A（SP-A）及甘露糖结合凝集素（MBL）是否与耳道球菌相互作用。SP-A和MBL均以Ca(2+)依赖的方式与耳道球菌结合。耳道球菌可诱导U937细胞分泌白细胞介素-8（IL-8），并在转染TLR2的人胚肾293（HEK293）细胞中激活核因子κB（NF-κB）。然而，转染了突变型TLR2（P681H）的细胞对耳道球菌无反应。此外，耳道球菌与细胞外TLR2结构域的重组可溶性形式共同沉淀，表明该细菌可直接与TLR2结合。SP-A和MBL增强了J774A.1细胞对耳道球菌的吞噬作用。当岩藻依聚糖和聚肌苷酸共同孵育时，凝集素刺激的耳道球菌吞噬作用显著减弱。免疫印迹分析显示，MBL存在于中耳炎患者的中耳积液中。这些结果表明，耳道球菌是凝集素和TLR2的配体，且凝集素可增强巨噬细胞对耳道球菌的吞噬作用，提示凝集素和TLR2在中耳针对耳道球菌感染的固有免疫中发挥重要作用。
