Klein R D, Su G L, Schmidt C, Aminlari A, Steinstraesser L, Alarcon W H, Zhang H Y, Wang S C
Department of Surgery, University of Michigan, Ann Arbor, Michigan 48109-0666, USA.
J Surg Res. 2000 Dec;94(2):159-66. doi: 10.1006/jsre.2000.5975.
The first step in bacterial clearance by leukocytes is attachment and phagocytosis. Although lipopolysaccharide-binding protein (LBP) is best known for potentiating LPS-induced cytokine production through a CD14-dependent pathway, recent studies suggest that LBP plays a critical role in clearance of gram-negative bacteria and is essential for survival after bacterial challenge. We therefore sought to examine LBP's effect on Escherichia coli phagocytosis by alveolar macrophages (AMs) and to determine if this effect is mediated through CD14.
Phosphatidylinositol-specific phospholipase C (PIPLC)-treated and untreated rat AMs were incubated in the presence of increasing doses of recombinant LBP or negative control protein (choramphenicol acetyltransferase) prior to E. coli-FITC (Ec-F) BioParticle challenge. Phagocytosed bacteria were assayed by fluorescence measurement. A time course study was also performed.
LBP potentiated phagocytosis of Ec-F BioParticles by AMs in a dose-dependent fashion. Kinetic studies showed that LBP augmented Ec-F phagocytosis by 76% at 30 min. Treatment of AMs with PIPLC to remove CD14 resulted in only a partial decrease in LBP-mediated enhancement of phagocytosis.
These results clearly demonstrate that LBP plays an important role in enhancing Ec-F binding and phagocytosis in a time- and dose-dependent manner. This observed increase may not require the presence of CD14 as significant potentiation of phagocytosis still occurred after PIPLC treatment. We postulate that the LBP-mediated increase in Ec-F phagocytosis can occur in the absence of CD14 through the presence of another receptor.
白细胞清除细菌的第一步是黏附和吞噬作用。尽管脂多糖结合蛋白（LBP）因通过CD14依赖途径增强脂多糖诱导的细胞因子产生而最为人所知，但最近的研究表明，LBP在革兰氏阴性菌清除中起关键作用，并且在细菌攻击后存活中至关重要。因此，我们试图研究LBP对肺泡巨噬细胞（AM）吞噬大肠杆菌的影响，并确定这种影响是否通过CD14介导。
在大肠杆菌-异硫氰酸荧光素（Ec-F）生物颗粒攻击之前，将经磷脂酰肌醇特异性磷脂酶C（PIPLC）处理和未处理的大鼠AM与递增剂量的重组LBP或阴性对照蛋白（氯霉素乙酰转移酶）一起孵育。通过荧光测量分析吞噬的细菌。还进行了时间进程研究。
LBP以剂量依赖方式增强AM对Ec-F生物颗粒的吞噬作用。动力学研究表明，LBP在30分钟时使Ec-F吞噬作用增强了76%。用PIPLC处理AM以去除CD14，仅导致LBP介导的吞噬作用增强部分降低。
这些结果清楚地表明，LBP在以时间和剂量依赖方式增强Ec-F结合和吞噬作用中起重要作用。观察到的增加可能不需要CD14的存在，因为在PIPLC处理后吞噬作用仍有显著增强。我们推测，在没有CDl4的情况下，通过另一种受体的存在，LBP介导的Ec-F吞噬作用增加仍可发生。
