Effect of free radical altered IgG on allergic inflammation

The rheumatoid synovium is capable of producing large amounts of IgG which may become modified by the actions of free radicals. A rat model of synovitis was established and challenged with both normal and free radical altered IgG. IgG was prepared from homologous pooled serum by high performance liquid chromatography, and free radical damage was induced by 15 minutes ultraviolet (UV) irradiation. The results showed a worsening in gross assessments of inflammation, increases in biochemical indices of lipid peroxidation, and also a rise in the proportion of IgG which, on reisolation, showed the characteristic fluorescence associated with free radical damage. This demonstrated how the presence of free radical altered IgG might convert an inflammatory insult to a more persistent stimulus, and the capacity of an environment subjected to continuing antigenic stimulation to induce further free radical damage to IgG.