Demonstration of anti-idiotypic antibodies directed against IgM rheumatoid factor in the serum of rheumatoid arthritis patients.
We have identified the presence of anti-idiotypic activity against IgMRF in the sera of RA patients. Only patients seropositive for IgMRF had significant levels of anti-idiotypic activity, while seronegative patients and normal volunteers did not. When this anti-idiotypic activity was affinity-purified from a single RA patient, two separate binding activities were identified. IgG antibodies were pepsin-digested to F(ab')2 fragments before affinity-purification to remove the Fc portion capable of binding to IgMRF. Anti-idiotypic F(ab')2 fragments of IgG were eluted from an IgMRF-Sepharose 4B column. These F(ab')2 bound preferentially to IgMRF bearing an idiotype recognized by the anti-idiotypic murine monoclonal 17.109. A second anti-idiotypic F(ab')2 was affinity purified using rabbit anti-human Fc antibody bound to Sepharose 4B. These eluted antibodies behaved as the internal image of IgG, binding five out of seven IgMRF's tested. The binding of both anti-idiotypic F(ab')2 was inhibited with human IgG. The presence of both IgMRF and anti-idiotypic antibodies directed against it in the sera of RA patients suggests that anti-idiotypic antibodies alone are not capable of inhibiting the production of rheumatoid factor.
Hancock
W K
WK
Department of Pathology, University of California, Los Angeles.
Barnett
E V
EV
D001172:Arthritis, Rheumatoid / Q000276:immunology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000032:analysis; D007074:Immunoglobulin G / Q000032:analysis; D007130:Immunoglobulin Idiotypes / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D012217:Rheumatoid Factor / Q000276:immunology*
D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D012217:Rheumatoid Factor