title: Two Ia.17-specific monoclonal antibodies detect the same epitope but do not share idiotype.
abstract: The clonal diversity of anti-Ia antibodies was studied by using heterologous anti-idiotypic reagents generated against two Ia.17-specific monoclonal antibodies (Mab). The Mab 10-2.16 and 10-3.6 are specific for the Ia.17 public specificity expressed on I-A molecules of the k, s, f, u, r, and j haplotypes. Competitive inhibition experiments demonstrated that 10-2.16 and 10-3.6 inhibited the binding of each other to Ia.17-positive cell targets, indicating that they detected the same or overlapping epitope(s). Identical inhibition patterns of 125I-10-2.16 binding by 10-3.6 by using Ia.17-positive target cells of four different strains indicated that inhibition was not due to steric hindrance from binding to spatially related epitopes. Rabbit anti-10-2.16 serum detected both site-specific and framework-specific 10-2.16 idiotypic determinants not shared by 10-3.6. Conversely, rabbit anti-10-3.6 serum detected 10-3.6 idiotypic determinants not shared by 10-2.16. C3H/J (I-Ak) anti-10-2.16 serum detected only 10-2.16 framework-specific idiotypes, suggesting that 10-2.16 site-specific determinants represent cellular determinants for syngeneic Ia antigens. Furthermore, anti-Ia.17 immune serum from three of 10 mice with the Igh-Cb allotype expressed the 10-2.16 framework-specific idiotype. We have demonstrated that two anti-Ia.17 Mab, 10-2.16 and 10-3.6, lack a shared idiotype, even though they detect a similar epitope. This observation and the variable expression of 10-2.16 idiotypic determinants in immune sera indicate that the B cell response to the Ia.17 epitope detected by 10-2.16 and 10-3.6 is diverse.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000502:physiology; D000916:Antibody Diversity; D001667:Binding, Competitive; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007130:Immunoglobulin Idiotypes / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D011817:Rabbits; D013045:Species Specificity
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D007130:Immunoglobulin Idiotypes