[Histopathogenesis of synovialitis in experimental allergic rabbit arthritis. Comparative studies on rheumatoid...

The development of synovitis was studied in 64 rabbits with experimentally produced allergic arthritis and in 30 rabbits with experimentally produced non-allergic arthritis. The results are compared with the morphological changes of the synovial membrane in rheumatoid arthritis, especially in early stages, known from the literature. The experimentally produced non-allergic arthritis shows no similarity whatsoever to rheumatoid arthritis. On the other hand, there is a pronounced similarity of the synovitis in experimentally produced allergic arthritis and in the fully developed stage of rheumatoid arthritis. In experimental allergic arthritis this stage is already reached after three weeks while the changes in the synovial membrane in rheumatoid arthritis are only little characteristic over a disease period of up to six months. A subdivision of individual morphological criteria shows special differences in the vascular changes and in the ratio of lymphocytes to plasma cells. In experimentally produced allergic arthritis, there is only initially a thrombovasculitis within the frame of the Arthus reaction whereas in rheumatoid arthritis, especially in the early stages, a proliferative vasculitis is frequently described. Furthermore, in experimentally produced allergic arthritis as compared to rheumatoid arthritis, the plasma cells are preponderating over the lymphocytes, which points to an increased humoral immune response in the animal model.