Normal human serum was depleted of factor H by immunoaffinity chromatography. The product is tested for the absence of factor H by double immunodiffusion. Factor H is a regulator of complement activation. As a result, factor H-Dpl is still capable of activating the alternative pathway and does so spontaneously and very rapidly in the absence of factor H. In fact, activation occurs in less than 2 min in the fluid phase without an activating particle resulting in the consumption of both C3 and factor B. For this reason this depleted serum is stored with 0.1 mM EDTA to inhibit spontaneous activation. Factor H-Dpl is certified to possess a functional alternative pathway for complement activation only if a controlling factor, such as factor H, is added prior to the addition of metal ions (specifically Mg++). Full reconstitution requires addition of 500 µg factor H/mL serum. It is also tested for and certified to contain functional classical pathway indicating that all other complement components necessary for classical and alternative pathway activation are present except for factor H (Morgan, B.P. (2000); Dodds, A.W. and Sim, R.B. (1997)).
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