Peroxidase arthritis. I. An immunologically mediated inflammatory response with ultrastructural cytochemical localization of antigen and specific antibody.

Synovitis was produced in rabbits by daily intra-articular injections of the heterologous antigen horseradish peroxidase. The resulting "peroxidase arthritis" resembled rheumatoid arthritis histologically. Many of the subsynovial plasma cells, plasmablasts and immunoblasts contained specific antibody to horseradish peroxidase; the remainder appeared to contain immunoglobulins of other specificities. Peroxidase arthritis has unique advantages for the study of the cellular and subcellular events in the pathogenesis of the local immune inflammatory response to heterologous antigen. Antigen and specific antibody can be localized precisely by ultrastructural cytochemical technics. The reaction can be terminated at any stage, permitting observation of the early events in its pathogenesis.