Complement activation in factor D-deficient mice
Complement activation in factor D-deficient mice
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DOI：
10.1073/pnas.261428398
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发表时间：
2001-12-04
影响因子：
11.1
通讯作者：
Volanakis, JE
中科院分区：
文献类型：
--
作者：
Xu, YY;Ma, MH;Volanakis, JE
为了评估替代途径在补体激活和宿主防御中的贡献及其在体内系统能量平衡调节中的可能作用，通过基因靶向产生了 D 因子缺陷小鼠。突变小鼠的发育没有明显异常，其体重与 D 因子充足的同窝小鼠相似。补体激活不能在缺陷小鼠的血清中通过旁路途径激活剂兔红细胞和酵母聚糖启动。令人惊讶的是，注射眼镜蛇毒因子（CVF）引起血清 C3 水平显着且可重复的降低，然而，正如预期的那样，在接受类似治疗的 B 因子缺陷小鼠中，C3 水平没有降低。 CVF 体外 C3 和 B 因子激活研究表明，在缺乏 D 因子的血清中，C3 的 α 链在 60 分钟内逐渐裂解，而没有检测到 B 因子的裂解。缺乏血清中的 CVF 依赖性 C3 裂解需要 Mg2+ 的存在，而在正常小鼠血清中不需要二价阳离子的存在。这些结果表明，在小鼠中，因子 D 对因子 B 的蛋白水解裂解并不是酶原向 CVF 结合因子 B 的活性酶构象转变的绝对要求。在因子 D 缺乏的血清中，C3 片段对肺炎链球菌的调理作用动力学要慢得多，这表明感染后早期替代途径对抗菌宿主防御的重要贡献。
To assess the contribution of the alternative pathway in complement activation and host defense and its possible role in the regulation of systemic energy balance in vivo, factor D-deficient mice were generated by gene targeting. The mutant mice have no apparent abnormality in development and their body weights are similar to those of factor D-sufficient littermates. Complement activation could not be initiated in the serum of deficient mice by the alternative pathway activators rabbit erythrocytes and zymosan. Surprisingly, injection of cobra venom factor (CVF) caused a profound and reproducible reduction in serum C3 levels, whereas, as expected, there was no C3 reduction in factor B-deficient mice treated similarly. Studies of C3 and factor B activation in vitro by CVF demonstrated that in factor D-deficient serum the a chain of C3 was cleaved gradually over a period of 60 min without detectable cleavage of factor B. CVF-dependent C3 cleavage in the deficient serum required the presence of Mg2+, whereas in normal mouse serum the presence of divalent cations was not required. These results suggest that in mouse proteolytic cleavage of factor B by factor D is not an absolute requirement for the zymogen to active enzyme conformational transition of CVF-bound factor B. Kinetics of opsonization of Streptococcus pneumoniae by C3 fragments was much slower in factor D-deficient serum, suggesting a significant contribution of the alternative pathway to antibacterial host defense early after infection.