Kinetic analysis of interaction of different types of rheumatoid factors with immobilized IgG using surface plasmon resonance

Rheumatoid factors (RFs) are autoantibodies, which recognize antigens on a constant region of immunoglobulin G (IgG), Among various RF classes, RF of the IgG class (IgGRF) forms immune complexes in rheumatoid joints and is im plicated in the pathogenesis of rheumatoid arthritis (RA), To characterize the formation of IgGRF immune complexes, in the present study, IgGRF was is olated from sera of RA patients, and its interaction with immobilized IgG w as analyzed and compared to that of IgMRF or IgARF by means of surface plas mon resonance. On gel filtration, the IgGRF was eluted as a single peak cor responding to IgG, excluding the possible formation of self-associating IgG RF complexes in solution. Sensorgrams of the interaction of IgGRF with immo bilized IgG revealed that it clearly bound to the IgG at 6 degreesC, but no t at 30 degreesC, The degree of interaction decreased inversely with an inc rease in temperature, suggesting that IgGRF is much more reactive at lower temperatures. In contrast, the interaction of IgARF and IgMRF with IgG at 6 degreesC was similar to that at 30 degreesC. The association rate constant (k(a)) of IgGRF decreased with an increase in temperature, while those of IgARF and IgMRF were similar under various thermal conditions. The dissocia tion rate constant (k(d)) of IgGRF was greatly reduced at 25 degreesC, but those of IgARF and IgMRF slightly increased with an increase in temperature , These results suggested that the mode of interaction of IgGRF with IgG di ffered from in the cases of IgMRF and IgARF, The kinetic properties of the IgGRF-IgG interaction may facilitate elucidation of the IgGRF immune comple x formation in rheumatoid joints.