Brandenburg Klaus, Howe Jörg, Gutsman Thomas, Garidel Patrick
Forschungszentrum Borstel, Leibniz-Zentrum für Medizin und Biowissenschaften, Borstel, Germany.
Curr Med Chem. 2009;16(21):2653-60. doi: 10.2174/092986709788682001.
Lipopolysaccharides (LPS, endotoxins) belong to the strongest elicitors of the mammalian immune system due to the induction of a series of cytokines such as tumor-necrosis-factor-alpha (TNFalpha) in immunocompetent cells like mononuclear cells. Since the effects of LPS on human health may be pathologically at too high concentrations (e.g., septic shock syndrome), it is of uttermost importance to have a reliable assay for measuring the concentrations of endotoxins in vitro and in vivo (human body fluids). The activation of the clotting cascade from the horseshoe crab (Limulus polyphemus), the Limulus amoebocyte lysate test (LAL), has been the standard and most sensitive assay to detect bacterial endotoxins. However, there are restrictions with this test. It was found in some clinical trials that the results from the LAL test did not correlate with the presence of bacteremia due to Gram-negative organisms or with the mortality but correlated with the presence of fungal bloodstream infections. This resulted from the fact that the LAL assay does not only respond to bacterial endotoxins but is activated also by (1-->3)-beta-D-glucan. Furthermore, in extensive studies the structural requirements for activation of the LAL test were analyzed, and it was found that the LAL activity correlated with pyrogenicity but not with activation of the complement cascade. Furthermore, there was no correlation of the LAL activity with cytokine expression (for example tumor-necrosis-factor-alpha and interleulkins-1 and 6) in mononuclear cells when the 4/2 acyl chain pattern of enterobacterial lipid A was changed, or when the cytokine production induced by LPS from various different species in the whole blood assay was compared with the response from the LAL test. To clarify the questions raised by the different experimental findings, data from literature are summarized to get a more closer insight where the Limulus test confidentially monitors the endotoxicity of LPS and other compounds and where this is not the case, and which are the decisive epitopes for recognition of the LPS molecules. These data are very crucial for example in clinical tests, whether the LAL assay can reliably describe the effectivity of an antibacterial therapy.
脂多糖（LPS，内毒素）是哺乳动物免疫系统最强的诱导剂之一，因为它能在单核细胞等免疫活性细胞中诱导一系列细胞因子，如肿瘤坏死因子-α（TNFα）。由于高浓度的LPS对人类健康可能产生病理影响（如脓毒症休克综合征），因此拥有一种可靠的检测方法来测量体外和体内（人体体液）内毒素浓度至关重要。鲎（美洲鲎）凝血级联反应的激活，即鲎试剂检测（LAL），一直是检测细菌内毒素的标准且最灵敏的检测方法。然而，该检测存在局限性。在一些临床试验中发现，LAL检测结果与革兰氏阴性菌引起的菌血症存在与否或死亡率无关，但与真菌血流感染的存在相关。这是因为LAL检测不仅对细菌内毒素有反应，还会被（1→3）-β-D-葡聚糖激活。此外，在广泛的研究中分析了LAL检测激活的结构要求，发现LAL活性与致热原性相关，但与补体级联反应的激活无关。此外，当改变肠杆菌脂多糖A的4/2酰基链模式时，或者在全血检测中比较不同物种的LPS诱导的细胞因子产生与LAL检测的反应时，LAL活性与单核细胞中的细胞因子表达（如肿瘤坏死因子-α和白细胞介素-1及-6）也没有相关性。为了阐明不同实验结果提出的问题，总结文献数据以更深入了解鲎试剂检测能可靠监测LPS和其他化合物内毒素毒性的情况以及不能监测的情况，以及识别LPS分子的决定性表位。例如在临床试验中，这些数据对于LAL检测能否可靠描述抗菌治疗的有效性非常关键。
