Watford W T, Ghio A J, Wright J R
Department of Cell Biology, Duke University Medical Center, Durham North Carolina 27710, USA.
Am J Physiol Lung Cell Mol Physiol. 2000 Nov;279(5):L790-8. doi: 10.1152/ajplung.2000.279.5.L790.
Complement is a system of plasma proteins that aids in the elimination of pathogens from the body. We hypothesized that there is a functional complement system present in the lung that aids in the removal of pathogens. Western blot analysis revealed complement proteins of the alternative and classical pathways of complement in bronchoalveolar lavage fluids (BALF) from healthy volunteers. Functional classical pathway activity was detected in human BALF, but there was no significant alternative pathway activity in lavage fluid, a finding that correlates with the low level of the alternative pathway protein, factor B, in these samples. Although the classical pathway of complement was functional in lavage fluid, the level of the classical pathway activator C1q was very low. We tested the ability of the lung- specific surfactant proteins, surfactant protein A (SP-A) and surfactant protein D (SP-D), to substitute for C1q in classical pathway activation, since they have structural homology to C1q. However, neither SP-A nor SP-D restored classical pathway activity to C1q-depleted serum. These data suggest that the classical pathway of complement is functionally active in the lung where it may play a role in the recognition and clearance of bacteria.
补体是一种血浆蛋白系统，有助于从体内清除病原体。我们推测肺中存在一种功能性补体系统，有助于清除病原体。蛋白质印迹分析显示，健康志愿者支气管肺泡灌洗液（BALF）中存在补体替代途径和经典途径的补体蛋白。在人BALF中检测到功能性经典途径活性，但灌洗液中没有明显的替代途径活性，这一发现与这些样本中替代途径蛋白B因子的低水平相关。尽管补体经典途径在灌洗液中具有功能，但经典途径激活剂C1q的水平非常低。我们测试了肺特异性表面活性物质蛋白，即表面活性物质蛋白A（SP-A）和表面活性物质蛋白D（SP-D），在经典途径激活中替代C1q的能力，因为它们与C1q具有结构同源性。然而，SP-A和SP-D均未将经典途径活性恢复至C1q缺失的血清中。这些数据表明，补体经典途径在肺中具有功能活性，可能在细菌的识别和清除中发挥作用。
