title: Competition between antigen and anti-idiotypes for rheumatoid factors.
abstract: Many idiotypic determinants on antibody molecules are thought to be located at the antigen binding site, and therefore the interaction between idiotype (Id) and anti-idiotype (anti-Id) is expected to be inhibited by the antigen. We describe two IgG and one IgM rheumatoid factors whose interactions with their respective anti-Id could only be partially inhibited by very large amounts of antigen, i.e., normal IgG. The anti-Id, however, readily inhibited the binding of their respective rheumatoid factors to IgG. The differences in interaction energies resulted in failure of antigen to readily block the Id-anti-Id interaction, and did not mean that the Id was not at the antigen combining site. The association constants for the Id-anti-Id interactions varied from 1.3 to 14.8 X 10(7) M-1, whereas the strength of the rheumatoid factor antigen bond is on the order of 10(5) M-1 for interaction with monomeric IgG. In addition, the anti-Id were able to remove rheumatoid factors that were bound to solid phase IgG, indicating that anti-Id have the potential for disrupting the immune complexes formed by antigen and antibody.
mesh_terms: D000818:Animals; D000915:Antibody Affinity; D000918:Antibody Specificity; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology* / Q000378:metabolism / Q000502:physiology; D007130:Immunoglobulin Idiotypes / Q000276:immunology* / Q000378:metabolism / Q000502:physiology; D007075:Immunoglobulin M / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D011817:Rabbits; D012217:Rheumatoid Factor / Q000378:metabolism*
chemical_list: D007074:Immunoglobulin G; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D012217:Rheumatoid Factor