He Haiqi, Genovese Kenneth J, Nisbet David J, Kogut Michael H
Southern Plains Agricultural Research Center (SPARC), USDA-ARS, College Station, TX 77845, USA.
Mol Immunol. 2006 Mar;43(7):783-9. doi: 10.1016/j.molimm.2005.07.002. Epub 2005 Aug 10.
Toll-like receptors (TLRs) play a major role in the innate immune system for initial recognition of microbial pathogens and pathogen associated components. Nitric oxide (NO) is generated in immune cells in response to microbial stimulation and is involved in pathogenesis and control of infection. We used RT-PCR analysis to examine the TLR expression profile on chicken monocytes and demonstrated these cells express chicken TLR2, 3, 4, 6, and 7. TLR5 was not detected by the TR-PCR. We also investigated the differential induction of NO synthesis in chicken monocytes by TLR agonists, including flagellin (FGN, from Salmonella typhimurium), synthetic lipoprotein Pam3CSK4 (PAM), lipopolysaccharide (LPS, from Salmonella enteritidis), lipoteichoic acid (LTA, from Staphylococcus aureus), the synthetic double stranded RNA analog (poly I:C), the guanosine analog, loxoribine (LOX), and synthetic CpG oligodeoxydinucleotide (CpG-ODN). Our results indicate that there was a vast difference among these agonists for their ability to induce NO production. CpG-ODN and LPS were the most potent stimuli and induced significant quantities of NO in cultured monocytes, whereas LTA stimulated significant NO production only at high concentrations. Other agonists such as FGN and poly I:C stimulated very little NO, while PAM, LOX, and nCpG-ODN (control ODN) did not induce NO production. RT-PCR analysis demonstrated that LPS, LTA, and CpG-ODN induced inducible nitric oxide synthase (iNOS) expression in monocytes; whereas the other agonists did not. The presence of TLRs on chicken monocytes and the differential induction of NO production in chicken monocytes by various TLR agonists suggest the differentiation of signaling pathways downstream of individual TLRs.
Toll样受体（TLRs）在天然免疫系统中发挥着重要作用，可对微生物病原体及病原体相关成分进行初始识别。一氧化氮（NO）在免疫细胞中因微生物刺激而产生，并参与发病机制及感染控制。我们采用逆转录聚合酶链反应（RT-PCR）分析来检测鸡单核细胞上的TLR表达谱，并证明这些细胞表达鸡TLR2、3、4、6和7。通过TR-PCR未检测到TLR5。我们还研究了TLR激动剂对鸡单核细胞中NO合成的差异诱导作用，这些激动剂包括鞭毛蛋白（FGN，来自鼠伤寒沙门氏菌）、合成脂蛋白Pam3CSK4（PAM）、脂多糖（LPS，来自肠炎沙门氏菌）、脂磷壁酸（LTA，来自金黄色葡萄球菌）、合成双链RNA类似物（聚肌胞苷酸，poly I:C）、鸟苷类似物洛索立宾（LOX）以及合成的CpG寡脱氧核苷酸（CpG-ODN）。我们的结果表明，这些激动剂在诱导NO产生的能力上存在巨大差异。CpG-ODN和LPS是最有效的刺激物，可在培养的单核细胞中诱导产生大量的NO，而LTA仅在高浓度时刺激产生显著量的NO。其他激动剂如FGN和poly I:C刺激产生的NO极少，而PAM、LOX和非甲基化CpG-ODN（对照ODN）不诱导NO产生。RT-PCR分析表明，LPS、LTA和CpG-ODN可诱导单核细胞中诱导型一氧化氮合酶（iNOS）表达；而其他激动剂则不能。鸡单核细胞上TLRs的存在以及各种TLR激动剂对鸡单核细胞中NO产生的差异诱导表明单个TLR下游信号通路的分化。
