Product Description

C3/FB-Depleted Serum is normal humanserum in which C3 and factor B(fB) have been removed by immunoaffinity chromatography.The product istested for the absence of C3 and factor B activity by testing classical and alternative pathway function and for the absence of C3 andfactorB proteins by double immunodiffusion. The C3/FB-depleted serumis certified to exhibitless than 5% classical pathway and alternativepathway activities. A functionalclassical pathway can be reconstitutedby addition of purified C3 protein (1.3mg/mL) whereas a functionalalternative pathway can be reconstituted byaddition of purified C3protein (1.3 mg/mL) and factor B protein (0.2 mg/mL)indicating thatall other complement components necessary for classical andalternativepathway activation are present. After reconstitution with C3 (1.3mgC3/mL) the C3/FB-Depleted Serum is certified to possess a functional classical pathway for complement activation whereas after reconstitutionwithC3 (1.3 mg C3/mL) and factor B (0.2 mg/mL), the product iscertified to possessa functional alternative pathway for complementactivation (Morgan, B.P.(2000); Dodds, A.W. and Sim, R.B. (1997)).Although a functional lectin pathwayshould also be reconstituted bythe addition of similar concentrations of C3,the function of thispathway is not tested.

Note that there is a weak C3by-passmechanism whereby the convertase C4b,C2a is able to activate C5(Rawal, N.& Pangburn, M.K. 2003) and form C5b-9 complexes capableof causing lowgrade lysis. This system of C5 activation is functionalin both the classicaland the lectin pathways and is approximately1000-fold less active than in thepresence of C3.

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Complement Technology的C1是级联反应中的第一个补体成分，称为补体经典途径。C1与抗原结合的抗体（免疫复合物）结合并被其激活，从而产生引发级联反应的蛋白酶。C1实际上是钙依赖性复合物中结合在一起的三种不同蛋白质（C1q，C1r和C1s）的非共价复合物。C1q通过其六个臂中的两个或多个与IgG或IgM的Fc结构域结合。多臂与免疫复合物的结合被认为会引入压力，从而导致复合物中的两个C1r蛋白（蛋白酶酶原）自身激活，从而产生两种活性的C1r丝氨酸蛋白酶（Morikis，D.和Lambris，JD（2005））。 。这些激活的C1r亚基裂解并激活复合物中的两个C1s蛋白酶酶原。活化的C1裂解补体成分C4，释放出C4a，并启动C4b与活化表面的共价连接。活化的C1也切割C2，并且C2的较大片段结合至表面附着的C4b，形成C4b，C2a，其为经典途径的C3 / C5转化酶。