C4-deficient guinea pigs were characterized in 1971 as being completely genetically and functionally deficient in C4 (Ellman, L. et al. (1970); Ellman, L. et al. (1971); Frank, M.M., et al. (1971)). This line of guinea pigs has been maintained and used extensively for the characterization of complement. In fact, these animals were a key element in the rediscovery and detailed characterization of the alternative pathway of complement (Ellman, L. et al. (1971); Frank, M.M., et al. (1971)). The product is tested for the absence of C4 by functional assays for classical pathway activity. C4-D guinea pig serum reconstituted with human C4 is certified to possess a functional classical pathway for complement activation after reconstitution (Morgan, B.P. (2000); Dodds, A.W. and Sim, R.B. (1997)). The absence of C4 would also be predicted to prevent complement activation by the lectin pathway, but the function of this pathway is not tested.
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