Acquired Drivers of Dysregulation of Complement in C3G
A number of different autoantibodies recognising complement components and their regulators have been identified in C3G. The most common finding is a C3 nephritic factor. These are antibodies that bind to and stabilise C3 convertase resulting in over-activity of the complement system. C3 nephritic factors are found in many cases C3G, typically in ~80% of cases of DDD and ~50% of cases of C3GN.
Autoantibodies to complement factor H can be found in ~ 15% of cases of C3G. Many of these have been shown to impair the regulatory function of FH resulting in over-activation of complement. More recently, autoantibodies have been identified to the complement components C3 and factor B. Studies have demonstrated their ability to cause dysregulation of complement.