Synovial inflammation induced by a local allergic reaction.

A rat model has been developed to examine the possible role of homocytotropic antibodies in initiating or exacerbating synovial inflammation. The technique, passive synovial anaphylaxis, involves passively sensitizing rat knee joints with specific IgE, then challenging intravenously with the corresponding antigen while monitoring for signs of inflammation. Swelling of the sensitized joints reached maximum 2 h after the challenge, then gradually decreased to prechallenge levels by 24 h. Radioisotopic joint scans detected a passive synovial anaphylaxis induced increase in local blood flow and exudation within the joints. The degree of swelling correlated directly with the amount of antigen specific IgE in the sensitizing serum, and individual joints remained sensitized for up to 36 days after the IgE injection.