Response of synovial immunocytes to intra-articular agents in experimental arthritis

In rabbits with immune arthritis the numbers of lymphoid aggregates and pyroninophilic and non-pyroninophilic cells per unit area of synovium were calculated from sections taken at various intervals after intra-articular drug injections. A model of immune arthritis based on the results is presented. In the active phase of the arthritis, plasma cells, plasmablasts and lymphoid aggregates proliferate, while the number of lymphocytes decreases. In the inactive phase after treatment, the cell pattern is the reverse. The ratio of pyroninophilic to non-pyroninophilic cells proved to be a good measure of the activity of the arthritis. A favourable therapeutic effect was achieved with triamcinolone hexacetonide and combined steroid-osmic acid, but not with osmic acid alone.