Barnum S R
Department of Microbiology, University of Alabama at Birmingham 35294, USA.
Crit Rev Oral Biol Med. 1995;6(2):132-46. doi: 10.1177/10454411950060020301.
Complement is an important effector arm of the human immune response. Binding of proteolytic fragments derived from activation of complement by specific receptors leads to responses as diverse as inflammation, opsonization, and B-cell activation. The importance of characterizing the expression and regulation of complement in the CNS is highlighted by growing evidence that complement plays a significant role in the pathogenesis of a variety of neurological diseases, such as multiple sclerosis and Alzheimer's disease. In vitro studies have demonstrated that astrocytes, the predominant glial cell type in the brain, are capable of expressing or producing a majority of the components of the complement system. Expression of many complement proteins synthesized by astrocytes is regulated by both pro- and anti-inflammatory cytokines, many of which are also produced by several cell types in the CNS. In addition to astrocytes, ependymal cells, endothelial cells, microglia, and neurons have recently been shown to synthesize various complement proteins or express complement receptors on their cell surfaces. Together, these studies demonstrate that several cell types throughout the brain have the potential to express complement and, in many cases, increase expression in response to mediators of the acute phase response. These studies suggest that complement may play a greater role in CNS immune responses than previously thought, and pave the way for better understanding of the dynamics of complement expression and regulation in vivo. Such understanding may lead to therapeutic manipulation of complement host defense functions in a variety of inflammatory and degenerative diseases in the CNS.
补体是人体免疫反应的一个重要效应分支。补体经特异性受体激活后产生的蛋白水解片段结合，可引发多种反应，如炎症、调理作用和B细胞激活。越来越多的证据表明补体在多种神经疾病（如多发性硬化症和阿尔茨海默病）的发病机制中起重要作用，这凸显了在中枢神经系统中表征补体表达和调控的重要性。体外研究表明，星形胶质细胞作为大脑中主要的神经胶质细胞类型，能够表达或产生补体系统的大部分成分。星形胶质细胞合成的许多补体蛋白的表达受促炎细胞因子和抗炎细胞因子的调控，其中许多细胞因子也由中枢神经系统中的多种细胞类型产生。除了星形胶质细胞，室管膜细胞、内皮细胞、小胶质细胞和神经元最近也被证明能合成各种补体蛋白或在其细胞表面表达补体受体。这些研究共同表明，大脑中的多种细胞类型都有表达补体的潜力，而且在许多情况下，会因急性期反应介质而增加表达。这些研究表明，补体在中枢神经系统免疫反应中可能发挥比以前认为的更大的作用，并为更好地理解体内补体表达和调控的动态过程铺平了道路。这种理解可能会导致在中枢神经系统的各种炎症和退行性疾病中对补体宿主防御功能进行治疗性调控。
