Autoantibody reactivity with short factor H fragments. Autoantibody binding to factor H fragments (corresponding to SCRs 1-4, 8-15, and 19-20) and a factor H–related protein 1 fragment (SCR 4-5) was assessed by the use of ELISA in a similar manner to the original autoantibody screen. Molar equivalent concentrations of the SCR fragments were coated onto separate ELISA plates, and a BSA subtraction was performed. Results are representative of 3 separate experiments.