A representative example demonstrating a humoral immune response against RGS19 in response to vaccination. Sera from patient number 10 was obtained before vaccination (left panel) and 1 month after vaccination (right panel) and incubated with E coli transfected with phage expressing myeloma-derived cDNA. Specific binding of antibody to recombinant proteins expressed on the lytic plaques was detected by incubation with alkaline phosphatase–conjugated goat anti–human IgG antibody. Antigen-antibody complexes were visualized by staining with 5-bromo-4-chloro-3-indolyl phosphate and nitro blue tetrazolium. Vaccination induced an antibody response directed against RGS19.