Anti-IgM antibody decreases dissociability of cell bound IgM anti-hapten antibodies as measured with fluid phase hapten.
We studied the effect of an IgG anti-IgM on the dissociation of cell bound IgM anti-hapten antibody, as measured with fluid phase hapten. Methotrexate (MTX) covalently bound to the red cells surface was used as hapten; rabbit anti-MTX IgM and rabbit anti-allotype IgG reactive with the IgM were used as antibodies. The amount of cell bound antibodies was measured with 125I-labelled protein A. In the absence of the anti-allotype antibody, most of the anti-hapten IgM was prevented from reassociation by fluid phase hapten. In the presence of the anti-allotype IgG most of the anti-hapten IgM was non-dissociable, with about a 1000-fold increase in the apparent binding constant. We found that (1) dissociability of the anti-hapten IgM depended on the density of the cell bound hapten, (2) decrease in dissociability was a function of the anti-allotype antibody concn and (3) even in the presence of excess anti-allotype antibody dissociability was an inverse function of anti-hapten IgM concn.
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D000915:Antibody Affinity; D000937:Antigen-Antibody Reactions; D001667:Binding, Competitive; D004306:Dose-Response Relationship, Immunologic; D006241:Haptens / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D008727:Methotrexate / Q000276:immunology; D011817:Rabbits; D012756:Sheep
D000888:Antibodies, Anti-Idiotypic; D006241:Haptens; D007075:Immunoglobulin M; D008727:Methotrexate