Activation of the alternative complement pathway with rabbit erythrocytes by circumvention of the regulatory action of endogenous control proteins
Activation of the alternative complement pathway with rabbit erythrocytes by circumvention of the regulatory action of endogenous control proteins
复制标题
通过规避内源性控制蛋白的调节作用激活兔红细胞的替代补体途径
DOI：
--
复制
发表时间：
1977
影响因子：
15.3
通讯作者：
K. Austen
中科院分区：
文献类型：
--
作者：
D. Fearon;K. Austen
补体旁路途径对C3的裂解至少发生在两个不同的阶段：通过天然C3、B、D和P的相互作用连续低等级产生C3 B，以及随后通过C3 B、B、D和P的相互作用扩增C3裂解，其形成扩增转化酶P、C3 b、B B。过渡到C3 b依赖性扩增是实现实质性C3裂解所必需的，并且通常受到C3 b灭活剂（C3 bINA）和β 1H的联合作用的限制。旁路途径的激活剂，如兔红细胞（E（r）），提供保护结合的C3 b和P、C3 b、Bb免受这些调节蛋白作用的位点，并允许通过低级液相反应沉积的C3 b组装膜相关扩增转化酶，其可以存款另外的受保护的C3 b。在对照蛋白质C3 bINA和β1H几乎完全灭活与绵羊红细胞（E（s））结合的C3 b（E（s）不激活旁路途径）的条件下，与E（r）结合的C3 b的功能减少不到五分之一。此外，E（r）上的P稳定扩增转化酶对β 1H介导的衰变解离的敏感性比E（s）上的转化酶低10倍。将E（r）加入到纯化的C3、B、D、P、C3 bINA和β 1 H的调节混合物中，通过在E（r）上形成扩增转化酶，导致C3和B的扩增失活，如其随后暴露于C3-C9的裂解所示。相反，E（s）没有将C3和B的低级别液相灭活推进到放大灭活，并且细胞没有转化为对C3- C9裂解敏感的中间体。由于E（r）和E（s）在不受调节的液相反应期间产生的C3 b的无效固定方面没有区别，因此E（r）的活化能力必须在于其保护结合的C3 b和P、C3 b、Bb免受调节蛋白的影响，而不是增强结合来自液相的C3 b的能力。当反应限于低等级流体相转换时，引入E（r）而不是E（s）导致C3 b沉积增加100倍，表明旁路途径的表面依赖性活化的特征在于C3 b在起始表面上的有效沉积。因此，活化表面将旁路途径蛋白质的相互作用推进到扩增阶段，因为调节蛋白质在沉积在这些表面上时不能选择性地处理它们的底物，并且导致不一定依赖于适应性免疫的特异性。
Cleavage of C3 by the alternative complement pathway occurs in at least two distinct phases: continuous low grade generation of C3b by the interaction of native C3, B, D, and P, and subsequent amplified cleavage of C3 by the interaction of C3b, B, D, and P which forms the amplification convertase, P,C3b,Bb. Transition to C3b-dependent amplification is necessary to achieve substantial C3 cleavage and is normally limited by the combined action of C3b inactivator (C3bINA) and βlH. An activator of the alternative pathway, such as rabbit erythrocytes (E(r)), provides sites that protect bound C3b and P,C3b,Bb from the action of these regulatory proteins and permits C3b deposited by the low grade fluid phase reaction to assemble a membrane-associated amplification convertase which can deposit additional protected C3b. Under conditions in which the control proteins, C3bINA and β1H, almost completely inactivated C3b bound to sheep erythrocytes (E(s)), which does not activate the alternative pathway, the function of C3b bound to E(r) was diminished by less than one-fifth. Further, the P- stabilized amplification convertase on E(r) was 10-fold less sensitive to β1H-mediated decay-dissociation than the convertase on E(s). The addition of E(r) to a regulated mixture of purified C3, B, D, P, C3bINA, and β1H resulted in amplified inactivation of C3 and B by formation of the amplification convertase on E(r) as indicated by its lysis with subsequent exposure to C3-C9. In contrast, E(s) did not advance the low grade fluid phase inactivation of C3 and B to amplified inactivation and the cell was not converted to an intermediate susceptible to lysis by C3- C9. Since E(r) and E(s) did not differ in their inefficient fixation of C3b generated during an unregulated fluid phase reaction, the activating capacity of E(r) must reside in its protection of bound C3b and P, C3b,Bb from the regulatory proteins rather than in enhanced capacity to bind C3b from the fluid phase. When the reaction is limited to low grade fluid phase turnover, introduction of E(r) but not E(s) results in a 100-fold increase in the deposition of C3b, indicating that surface-dependent activation of the alternative pathway is characterized by efficient deposition of C3b on the initiating surface. Thus, the activating surfaces advance the interaction of the alternative pathway proteins to the amplification phase because of the selective inability of the regulatory proteins to deal with their substrates when deposited on these surfaces and results in a specificity that is not necessarily dependent on adaptive immunity.