Complement System
补体系统是先天免疫系统的一部分，对提高机体免疫力、炎症、组织再生和其他生理进程起着非常重要的作用。补体激活不仅会引起病原体调理并被吞噬细胞清除，而且还会导致吞噬细胞和巨噬细胞的趋化现象。此外，补体系统还会形成终端抗体复合物(MAC)，一个膜通道引起相应的病原体发生渗透性溶解。当补体无法适应时，可补给获得性免疫系统并且包含于B和T细胞反应调节。
补体激活会根据病原体的自然特性展开三种不同长度的补体激活途径：常规途径、凝集素途径和旁路途径。以上三种途径均会汇聚到常规终端途径并形成MAC。此外，C3a和C5a灭活因子会诱发生理学上的多血症，导致发生化学反应范围内的脱噬作用。补体系统包含的30多种蛋白质为可溶于血液中的可溶性蛋白，抑或是与蛋白相关的膜。多数现有的不活跃酵素原随后会相继被分裂并激活。所有三种途径中的中体均为C3（血液中含量最多的补给蛋白）。补体激活涵盖C3a、C3b和C5a的激活形成以及最终的MAC。
补体激活除了上述三种稳定途径之外，因子（例如胰舒血管素、胞浆素、凝血酶）以及XIIa还可单独激活补体系统，这样不需要C3蛋白。
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Classical Pathway
C1QA (Complement Component 1, Q Subcomponent, A Chain):
C1QB (Complement Component 1, Q Subcomponent, B Chain):
C1QC (Complement Component 1, Q Subcomponent, C Chain):
C1R (Complement Component 1, R Subcomponent):
C1S (Complement Component 1, S Subcomponent):
C4 - Complement C4:
Lectin Pathway
MASP2 (Mannan-Binding Lectin serine Peptidase 2):
MASP1 (Mannan-Binding Lectin Serine Peptidase 1):
MBL2 (Mannose-Binding Lectin (Protein C) 2, Soluble):
FCN1 (Ficolin (Collagen/fibrinogen Domain Containing) 1):
FCN2 - Ficolin 2:
FCN3 (Ficolin (Collagen/fibrinogen Domain Containing) 3 (Hakata Antigen)):
Alternative Pathway
CFB - Complement Factor B:
C3 (Complement Component 3):
- Complement C3b:
CFH - Complement Factor H:
Terminal Pathway
C5 (Complement Component 5):
C7 (Complement Component C7):
C8A (Complement Component 8, alpha Polypeptide):
C8B (Complement Component 8, beta Polypeptide):
C8G (Complement Component 8, gamma Polypeptide):
C9 (Complement Component C9):
Regulators
CD55 (Complement Decay-Accelerating Factor):
SERPING1 (Serpin Peptidase Inhibitor, Clade G (C1 Inhibitor), Member 1):
CFI - Complement Factor I:
CR1 - CD35:
CFP (Complement Factor P):
C4BPA (Complement Component 4 Binding Protein, alpha):
C4BPB (Complement Component 4 Binding Protein, beta):
Extrinsic Pathway
F2 - Prothrombin:
PLG (Plasminogen):
KLK1 - Kallikrein 1:
KLK2 - Kallikrein 2:
PSA - Prostate Specific Antigen:
KLKB1 (Kallikrein B, Plasma (Fletcher Factor) 1):
KLK4 - Kallikrein 4:
KLK5 - Kallikrein 5:
KLK6 - Kallikrein 6:
KLK7 - Kallikrein 7:
KLK8 - Kallikrein 8:
KLK9 - Kallikrein 9:
KLK10 - Kallikrein 10:
PRSS57 (Protease, Serine, 57):
KLK11 - Kallikrein 11:
KLK12 - Kallikrein 12:
KLK13 - Kallikrein 13:
KLK14 - Kallikrein 14:
KLK15 - Kallikrein 15:
F12 (Coagulation Factor XII):
Complement Receptors
CR1L (Complement Component (3b/4b) Receptor 1-Like):
ITGAX - CD11c:
C3AR1 (Complement Component 3a Receptor 1):
CR1 - CD35:
C5AR1 (Complement Component 5a Receptor 1):
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