- Factor D will be measured by paired capture and detection antibodies (mAb D10/4 and biotinylated mAb I8/1) specific to factor D. The capture antibody used in the C3d assay (mAb I3/15) reacts with a neoepitope present on C3b, iC3b and C3dg and will be in combination with a biotinylated rabbit anti-C3d detection antibody for quantification of C3d. For all assays, incubation with the detection antibody will be followed by application of streptavidin-horseradish peroxidase conjugate. The substrate, 2 mM ABTS (2,2'-azino-di-(3-ethyl benzthiazolinesulfonate)) in buffer containing 2.5 mM peroxide, will be added and absorbance at 410 nm (490 nm reference) will be read using a microplate photometer. All samples will be run in triplicate.