Figure 3.

Identification of IgG4 anti-factor H autoantibodies: Plasma samples were analyzed for anti-factor H antibodies by a previously reported specific ELISA which was developed using Horse Radish peroxidase (HRP)-labeled secondary antibodies specific for human IgG, IgG4, and IgA, respectively (8). Data are shown as optic density at 490 nm (OD). (A) The patient’s serum was tested in duplicates at different dilutions 1:100, 1:400, and 1:1,000 for both IgG (black bars) and IgG4 (grey bars). Controls included a normal human serum (NHS), a serum with known elevated anti-CFH IgG levels, and a serum with elevated IgG4 but no anti-CFH activity. (B) Absence of IgA anti-factor H autoantibodies: Specific anti-CFH IgA antibodies were measured in the patient’s serum (total IgA level of 6.4 g/l), NHS, and another serum with a high total IgA concentration of 12.4 g/l.