Analysis of factor H, factor H–related protein 3, and factor H–related protein 1 in patients with factor H autoantibodies. Sera from subjects were run out on 10% SDS-PAGE and transferred to nitrocellulose. Factor H, factor H–related protein 3, and factor H–related protein 1 were then detected by staining as described in the Methods section. ECL Western blotting substrate was used to visualize bound antibody. Sera was available from all 13 patients (samples 1-13) for analysis of factor H and factor H–related protein 1, but only from 9 patients for factor H–related protein 3. These 9 samples plus control samples were run on parallel gels. A, B, and C are normal controls known to have 2 copies of CFHR1 and CFHR3. Data from the remaining 3 samples are shown on the right. Purified factor H (equivalent to 0.5 mg/mL) was used as a positive control (+) in the smaller antifactor H blot. Black vertical lines indicate a repositioned gel lane, and black boxes illustrate the individual blots used. This figure is representative of several independent experiments.