Private idiotypes on human polyclonal IgG anti-DNA antibodies are not expressed on coexisting IgM anti-DNA antibodies in systemic lupus erythematosus.
Sharing of private idiotypes (Id) on human polyclonal IgG anti-double-stranded DNA (dsDNA) with coexisting IgM anti-dsDNA was investigated using rabbit (R) anti-Id raised against IgG anti-dsDNA. The R-anti-Id showed specificity to private Id in or near the antigen-binding sites. The R-anti-Id poorly bound to the immobilized enriched IgM anti-dsDNA preparation but significantly bound to IgG anti-dsDNA preparation by a direct-binding ELISA (0.020 OD vs 0.295 OD, respectively). The R-anti-Id poorly inhibited the binding of IgM anti-dsDNA to immobilized dsDNA but significantly inhibited the binding of IgG anti-dsDNA to dsDNA (6% vs 55% inhibition, respectively). This was confirmed by poor inhibition of binding of the R-anti-Id to immobilized IgG anti-dsDNA by the enriched IgM anti-dsDNA preparation (maximum of 26% inhibition at 50 micrograms/ml). Nonsharing of private Id between IgG and coexisting IgM anti-dsDNA may represent the idiotypic diversity of human anti-DNA antibodies secondary to the frequent occurrence of somatic mutation on anti-DNA antibody during class switching.
Suenaga
R
R
Department of Internal Medicine, University of Kansas Medical Center, Kansas City 66103.
Abdou
N I
NI
D000818:Animals; D000974:Antibodies, Antinuclear / Q000032:analysis*; D000918:Antibody Specificity; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D002846:Chromatography, Affinity; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis*; D007130:Immunoglobulin Idiotypes / Q000032:analysis* / Q000276:immunology; D007075:Immunoglobulin M / Q000032:analysis*; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D011817:Rabbits; D013205:Staphylococcal Protein A
D000974:Antibodies, Antinuclear; D007074:Immunoglobulin G; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D013205:Staphylococcal Protein A