Chang N S, Boackle R J
Mol Immunol. 1985 Oct;22(10):1217-24. doi: 10.1016/0161-5890(85)90011-2.
The dilution of human serum in relatively low ionic strength buffer (mu = 0.070) caused the spontaneous activation of C1 and a limited activation of C4 and C3 in the fluid phase. The unusual degree of activation of the complement system in the fluid phase suggested that the optimal functions of complement-regulatory systems such as C1 inhibitor might be reduced. As a function of the time of preincubation (PI) of diluted serum at 37 degrees C, under low ionic strength conditions, an unusual complement-mediated hemolytic kinetic pattern was observed upon adding sensitized erythrocytes (EA). For a 1:36 dilution of human serum, there was an initial progressive decrease in complement hemolytic activity (from 3 to 20 min PI, phase I), followed by an apparent functional reversal (increase) in hemolytic activity (20-50 min PI, phase II) and finally a gradual irreversible depletion of the hemolytic activity (after 50 min PI, phase III). This hemolytic pattern could only be adequately demonstrated using a kinetic assay which followed the course of lysis of EA in the presence of low dilutions of human serum as a complement source. Others might have missed this observation due to the use of end-point titration methods which required the use of relatively elevated serum dilutions at the time of EA addition. Mechanisms which governed the variations in hemolytic activity at low ionic strength were not clear. Speculatively, partial consumption of early complement components, generation of free C1q and generation of complement fragments might have accounted for the initial decrease in the hemolytic activity observed in phase I. The apparent functional reversal of hemolytic activity observed in phase II might have involved a critical depletion of C1 inhibitor which occurred secondary to C1 inhibitor binding to C1 (activated by low ionic strength effects) and to the C1 activated at the time of EA addition. Without sufficient regulation, a rapid unrestricted C1-mediated complement activation could have occurred, which resulted in a rapid deposition of complement on the EA. Finally, prolonged exposure of serum to low ionic strength effects appeared to induce a significant complement consumption, which caused a time-dependent irreversible depletion of complement hemolytic activity (phase III). Excess exogenous C1 inhibitor, when co-incubated with diluted serum at low ionic strength, reversed the time-dependent effects of low ionic strength and enhanced the subsequent specific complement-mediated hemolytic activity as compared to controls.(ABSTRACT TRUNCATED AT 400 WORDS)
在相对低离子强度缓冲液（μ = 0.070）中对人血清进行稀释，会导致液相中C1自发激活以及C4和C3有限激活。液相中补体系统这种异常程度的激活表明，诸如C1抑制因子等补体调节系统的最佳功能可能会降低。作为在37℃下对稀释血清进行预孵育（PI）时间的函数，在低离子强度条件下，加入致敏红细胞（EA）后观察到一种异常的补体介导的溶血动力学模式。对于1:36稀释的人血清，补体溶血活性最初呈逐渐下降趋势（预孵育3至20分钟，第一阶段），随后溶血活性出现明显的功能逆转（增加）（预孵育20至50分钟，第二阶段），最后溶血活性逐渐不可逆地消耗殆尽（预孵育50分钟后，第三阶段）。这种溶血模式只有使用动力学测定法才能充分显示出来，该方法跟踪在低稀释度人血清作为补体来源存在的情况下EA的裂解过程。由于使用终点滴定法，在加入EA时需要使用相对较高的血清稀释度，其他人可能忽略了这一观察结果。低离子强度下控制溶血活性变化的机制尚不清楚。据推测，早期补体成分的部分消耗、游离C1q的产生以及补体片段的产生可能解释了在第一阶段观察到的溶血活性的初始下降。在第二阶段观察到的溶血活性的明显功能逆转可能涉及C1抑制因子的关键消耗，这是由于C1抑制因子与C1（因低离子强度效应而激活）以及在加入EA时激活的C1结合所致。如果没有足够的调节，可能会发生快速不受限制的C1介导的补体激活，导致补体在EA上快速沉积。最后，血清长时间暴露于低离子强度效应似乎会诱导显著的补体消耗，从而导致补体溶血活性随时间不可逆地消耗（第三阶段）。与对照组相比，当与低离子强度下的稀释血清共同孵育时，过量的外源性C1抑制因子可逆转低离子强度的时间依赖性效应，并增强随后特异性补体介导的溶血活性。（摘要截短至400字）
