Initial screening of sera was performed using retinal proteins that were extracted from a human retina, with 1% octyl glucoside in phosphate/saline buffer (PBS), pH 7.2. The proteins were separated by SDS-gel electrophoresis on a 10% gel and transferred to an Immobilon membrane (Millipore, Bedford, Massachusetts). Individual strips containing retinal proteins were blocked with 10% normal goat serum, 1% bovine serum albumin in PBS for 1 hr, and then probed with 1:100 diluted serum (1 hr) followed by a 1-hr incubation with anti-human IgG (H and L chain) conjugated to alkaline phosphatase (Sigma, St. Louis, MO). Color reaction was developed by adding the phosphatase substrate until dark bands, appeared in comparison to the positive control. Blots were run and examined in a masked fashion. As a positive control, we used a reference human serum containing anti-recoverin antibodies diluted 1:100. As a negative control, we omitted serum and applied only a secondary antibody.