Anticardiolipin (aCL) in sera from periodontitis subjects activate Toll-like receptor 4 (TLR4)

Anticardiolipin antibodies (aCL) have been reported to be present in 15–20% of sera from subjects with periodontitis at concentrations exceeding those found in 95% of the healthy adult population. These antibodies, albeit at concentrations exceeding those generally found in periodontitis subjects, are typically present in patients with the antiphospholipid syndrome (APS), an autoimmune disease characterized by thrombosis and recurrent pregnancy loss. aCL from APS patients are proinflammatory and can activate trophoblasts, macrophages, and platelets via cell-surface interactions with their target antigen beta-2-glycoprotein-I (β2GPI). β2GPI is an anionic phospholipid-binding serum protein that can associate with toll-like receptors (TLR’s) on the cell-surface, leading to cell activation following interaction with autoimmune aCL. We examined an expanded series of 629 sera from clinically characterized subjects for aCL content, and observed that 14–19% of these sera contained elevated (>95th %-tile) levels of aCL. We purified IgG from 16 subjects with elevated or normal levels of aCL and examined their ability to activate TLR2- or TLR4-transfected human embryonic kidney (HEK) cells, and observed that IgG from periodontitis patients with elevated aCL activated HEK-TLR4 cells, but not HEK-TLR2 cells. Prior removal of aCL by immunoabsorption significantly reduced the ability of IgG preparations from these sera to activate TLR4. Further experiments using a human first trimester trophoblastic cell line (HTR8 sv/neo) revealed that aCL from periodontitis patients stimulated IL-8 production, which was profoundly decreased if aCL was removed by immunoabsorption or if HTR8 sv/neo were pretreated with blocking anti-TLR4 antibodies. Thus, it appears that aCL from periodontitis patients can be proinflammatory, activating cells via TLR4. Since these antibodies are likely produced via molecular mimicry due to similarities between oral bacterial antigens and β2GPI, the data indicate that circulating serum aCL may induce or influence inflammatory responses at sites distant from the oral cavity.已有研究报道，15%~20%的牙周炎患者血清中存在抗心磷脂抗体（Anticardiolipin antibodies, aCL），其浓度高于95%健康成年人群的血清aCL水平。尽管抗磷脂综合征（Antiphospholipid syndrome, APS）患者体内的aCL浓度通常高于牙周炎患者，但该综合征是一类以血栓形成与复发性流产为特征的自身免疫性疾病，其患者体内普遍存在aCL。抗磷脂综合征患者体内的aCL具有促炎活性，可通过与靶抗原β2糖蛋白I（beta-2-glycoprotein-I, β2GPI）的细胞表面结合，激活滋养层细胞、巨噬细胞与血小板。β2GPI是一种可结合阴离子磷脂的血清蛋白，能够与细胞表面的Toll样受体（Toll-like receptors, TLRs）结合，在与自身免疫性aCL结合后引发细胞活化。本研究针对经临床表型鉴定的629份血清样本开展扩展队列检测，分析其aCL水平，结果显示其中14%~19%的血清aCL水平高于95百分位数阈值。研究人员从16名aCL水平升高或正常的受试者中纯化了免疫球蛋白G（IgG），并检测其激活转染了TLR2或TLR4的人胚肾（HEK）细胞的能力，结果发现，aCL水平升高的牙周炎患者的IgG可激活HEK-TLR4细胞，但无法激活HEK-TLR2细胞。通过免疫吸附法预先去除aCL后，这些血清来源的IgG制剂激活TLR4的能力显著降低。进一步使用人早孕滋养层细胞系（HTR8 sv/neo）开展的实验显示，牙周炎患者来源的aCL可刺激白细胞介素8（IL-8）的产生；若通过免疫吸附法去除aCL，或预先用阻断性抗TLR4抗体处理HTR8 sv/neo细胞，该IL-8分泌现象会显著减弱。综上，牙周炎患者体内的aCL具有促炎活性，可通过TLR4通路激活细胞。由于这类抗体可能通过口腔细菌抗原与β2GPI之间的分子模拟机制产生，本研究数据提示，循环血清aCL可能诱导或影响口腔以外部位的炎症应答。