Human factor D of the alternative pathway: purification and quantitation by enzyme amplified electroimmunoassay.

Purified factor D was prepared with a yield of about 30%. Monospecific antiserum was raised in rabbits. Immunochemical quantitation of factor D in serum and plasma was performed by electroimmunoassay and a sensitive staining technique based on enzyme amplification. Peroxidase-labeled swine antibodies to rabbit immunoglobulin were applied to the gel after electrophoresis. Immune precipitates were then visualized by staining for peroxidase activity. Factor D could be detected at 50 micrograms/l. The normal concentration of D in serum was 1.6 mg/l, as assessed by this assay.