Complement Factor P (Properdin) Functional Assay
Complement Factor P (Properdin) Functional Assay Developed and Manufactured by Svar Life Science
Size: 1×96 wells
Range: 0 – 200% relative activity
Incubation Time: 4 hours
Sample Type: Serum, EDTA Plasma
Sample Size: 50 µL
Alternative Names: Complement Factor P, Properdin
For Research Use Only
Factor P (Complement P, Properdin, FP) is a positive regulator and an initiator of the alternative pathway (AP) for complement activation. It binds surface-bound C3 and C5 convertases and stabilizes them to amplify the activation cascade. Factor P binding increases the half-life of the convertase complex approximately 10-fold. It is suggested, however debated, that Factor P also can initiate complement activation by binding for example cell surfaces or certain biological substrates, recruiting C3b or C3(H2O) and Factor B, and thus initiate the AP pathway. Factor P opposes the negative regulation of Factor H that enhances the dissociation of C3b and Bb and mediates Factor I cleavage of C3b to the inactive iC3b3 (Figure 1). Factor P is not produced in hepatocytes as most complement proteins, but instead by several cell types including monocytes, macrophages, T-cells and granulocytes. It is likely that transient increased concentration of Factor P enhances the AP upon local stimuli. For example, neutrophils have Factor P-containing granules that are secreted upon stimulation and can enhance the platelet-granulocyte aggregate formation. In plasma, Factor P is present in a concentration of approximately 4-25 µg/mL. Factor P is an elongated 53 kDa glycoprotein that oligomerizes in vivo to dimers, trimers or tetramers (P2, P3 and P4) in a ratio of 26:54:20 (P2:P3:P4) in head to tail structures. The oligomeric state correlates with C3 convertase stabilizing function and distribution of oligomers affects the overall Factor P functionality. Mutations, deficiencies, protein levels as well as protein deposits of Factor P are connected to diseases and disorders summarized by Chen et al. Deficiencies generally increase the susceptibility for meningococcal disease and other infectious diseases. Altered serum levels have been associated with for example C3 glomerulopathy, Lupus Nephritis, sepsis and chronic heart failure and IgA nephropathy.
The Factor P (Properdin) Functional assay is an enzyme-linked immunosorbent assay (ELISA) that combines principles of the functional complement activity assays with the use of labelled antibodies specific for deposited complement proteins. The amount of deposited complement proteins is proportional to the functional activity of Factor P in the sample.