[Comparative study on rat arthritis induced by various immune mechanisms (author's transl)]

Experimental arthritis was induced in rats by the use of horse ferritin as an antigen. The pathological findings were studied and the mechanisms of inflammation were analyzed. Arthritis was induced through various mode of actions: 1. Arthus reaction (antigen-induced arthritis). 2. Passive Arthus reaction. 3. Reverse passive Arthus reaction. 4. Arthritis induced by intra-articular injection of immune complex, by either single shot or repeated injections. 5. Arthritis induced by anamnestic reaction. Arthritis induced by repeated injections of immune complex or that induced by anamnestic reaction exhibited mild chronic synovitis characterized by round cell infiltration without detectable acute phase of inflammation. Arthritis induced through other immunological mechanisms revealed a sequential course of acute synovitis characterized by accumulation of polymorphonuclear leucocytes (PMN) followed by gradual disappearance of PMN and alternative increase of round cells or plasma cells and proliferation of synovial lining cells. All types of arthritis subsided with mild fibrosis of the synovial tissue without lasting over a significantly long time. Although the successful production of a long-lasting chronic arthritis has been reported in rabbits, it was impossible to induce such long standing arthritis through this experiment. The chronicity of the arthritis induced through immunological mechanism may not simply be due to the long-standing retention of immune complex within the involved joint but also due to other factors such as the species of the test animals, the nature of antigen used and local factors produced through acute joint inflammation.