Action of D-penicillamine on immunocomplexes containing rheumatoid factor

The affinity between purified rheumatoid factors (RF) and native or heat aggregated human IgG has been studied in vitro by polarization fluorescence in the presence and in the absence of D-penicillamine. The value of the dissociation constant was the same using native and heat aggregated IgG suggesting that binding to the aggregated protein is not dependent on the exposure of a new determinant lacking in the native molecule. The results obtained in the presence of D-penicillamine suggest that the concentration of the drug necessary to get a pronounced effect on the apparent dissociation constant of the immunocomplex between IgG and RF is not reached in vivo, in clinical situations.