Tissue distribution of IgG Fc receptors.

The mechanism causing deposition of circulating immune complexes is largely unknown. The possible role of tissue IgG Fc receptors in immune complex localization has been evaluated using IgG coated ox RBC (ox erythrocyte antisera [EA]) as indicator particles. Cryostat tissue sections of normal human synovium, skin, kidney, choroid plexus, lung and uveal tract were examined for the presence of IgG Fc receptors, with human spleen used as a positive control. Ox EA were shown to bind to splenic red pulp. This binding could be almost completely blocked by heat aggregated human IgG. In none of the other normal tissues examined were IgG Fc receptors demonstrated. To investigate the possibility that inflamed tissues express Fc receptors, biopsy specimens of rheumatoid synovium and skin demonstrating vasculitis were studied. No ox EA binding to these tissues was noted. We concluded that IgG Fc receptors are probably not present in tissues that are targets for immune complex deposition and are therefore unlikely to play a role in this process.