Description
General Description
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.
Physical Characteristics
C4-D guinea pig serum is supplied as a clear, straw-colored liquid containing all proteins of normal guinea pig serum except complement component C4.
Function
The depleted serum is tested for remaining classical pathway activity by hemolytic assays using antibody-sensitized sheep erythrocytes (CompTech #B200). The depleted serum is reconstituted with human C4 (CompTech #A105) and retested to verify that a functional classical and alternative pathways are restored. The Certificate of Analysis provided with each lot gives a description of the assays and specific titers for the depleted and reconstituted sera compared to normal human serum.
Assays
The unit of classical pathway activity is the CH50. A similar unit, the C4H50, is used to quantitate the activity of C4 and C4-D guinea pig serum. A C4H50 unit is the amount of functional C4 needed to lyse 50% of 3 x 107 EA cells (antibody-sensitized sheep erythrocytes (CompTech #B200)) when that amount of C4 (CompTech #A105) is incubated with the recommended volume of C4-D guinea pig serum in GVB++ (CompTech #B100) in a total volume of 500 µL for 30 min at 37o C. This amount of C4 indicates the sensitivity of the assay for C4 which is typically less than 2 ng C4 with 10 µL C4-D guinea pig serum. See the Certificate of Analysis for lot specific values.
Applications
C4-D guinea pig serum is used to assay C4 activity in samples and to supply a serum unable to activate complement via the classical pathway. Note that C1 and C2 may still be activated in the absence of C4, but whereas there is a C2 by-pass system there does not appear to be an efficient C4 by-pass mechanism. Low level lysis of EA in C4-D guinea pig serum has been shown to require activation of the early classical and the alternative pathways (Wagner, E. et al. (1999)).