Clinical applications of immunofixation: detection and quantitation of complement activation

The methods currently in use for the detection and quantitation of complement activation products are slow and time consuming. We describe a method utilising immunofixation after agarose or cellulose acetate membrane electrophoresis which allows large batches of samples to be screened rapidly for the presence of activation products of C3 and factor B. Further, after immunofixation on agarose the conversion product may be quantitated by densitometry. This method gives similar results to those obtained by crossed immunoelectrophoresis. Using both this technique and crossed immunoelectrophoresis we have been able to confirm that C4 activation occurs during electrophoresis in the absence of EDTA and that in the presence of EDTA it is not demonstrable even in patients with active immune complex disease.