Novel approach to identifying autoantibodies in rheumatoid synovitis with a biotinylated human autoantigen library and the enzyme-labeled antigen method

► We developed a novel approach to identifying autoantibodies in RA synovitis. ► 2183 proteins in human autoantigen library were screened using RA synovia extract. ► Plasmacytes producing specific autoantibodies were visualized within the lesion. ► The enzyme-labeled antigen method was used for localizing autoantibody production. ► Autoantibodies to tripartite motif-containing 21 and F-box only protein 2 were shown.