Clonal relationships between thyroid-stimulating hormone receptor-stimulating antibodies illustrate the effect of hypermutation on antibody function.
Graves' disease is characterized by production of agonist antibodies to the thyroid-stimulating hormone receptor (TSHR), but knowledge of the genetic and somatic events leading to their aberrant production is limited. We describe the genetic analysis of two monoclonal antibodies (mAbs) with thyroid-stimulating activity (TSAb) obtained from a single mouse with experimental Graves' disease. The mAbs were class switched, but used the same rearrangement of immunoglobulin heavy chain, variable region (IGHV) and immunoglobulin light chain, variable region (IGLV) germline genes, implying a clonal relationship and derivation from a single precursor B-cell clone. The IGHV-region genes of the two mAbs underwent high degrees of somatic hypermutation by sharing numerous mutations before diverging, while the IGLV genes evolved separately. Interestingly, the mutations were present in both the complementarity-determining regions (CDRs) and the framework regions. The cloned IGHV and IGLV genes were confirmed to have TSAb properties in experiments in which they were expressed as recombinant Fabs (rFabs). In other experiments, we swapped the IGLV genes with IGHV genes by constructing chimeric rFabs and showed that the chimeras retained TSAb activities, confirming the close functional relatedness of the V-region genes. Importantly, the IGLV genes in chimeric rFabs had a dominant stimulatory effect at low concentrations, while the IGHV genes had a dominant effect at higher concentrations. Our findings demonstrate that, in experimentally immunized mice, multiple pathogenic antibodies to TSHR can arise from a single clone by a series of somatic mutations in the V-region genes and may give an insight into how such antibodies develop spontaneously in autoimmune Graves' disease.
Padoa
Carolyn J
CJ
Division of Gene and Cell Based Therapy, King's College London School of Medicine, London, UK.
Larsen
Sanne L
SL
Hampe
Christiane S
CS
Gilbert
Jacqueline A
JA
Dagdan
Elif
E
Hegedus
Laszlo
L
Dunn-Walters
Deborah
D
Banga
J Paul
JP
D000818:Animals; D000911:Antibodies, Monoclonal; D000916:Antibody Diversity / Q000235:genetics; D015551:Autoimmunity; D022801:Complementarity Determining Regions / Q000235:genetics; D004252:DNA Mutational Analysis; D032621:DNA Shuffling; D005818:Genetic Engineering; D006111:Graves Disease / Q000235:genetics / Q000276:immunology*; D006825:Hybridomas; D007143:Immunoglobulin Heavy Chains / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D007146:Immunoglobulin lambda-Chains / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D018828:Immunoglobulins, Thyroid-Stimulating / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D011989:Receptors, Thyrotropin / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000235:genetics; D027041:Somatic Hypermutation, Immunoglobulin
D000911:Antibodies, Monoclonal; D022801:Complementarity Determining Regions; D007143:Immunoglobulin Heavy Chains; D007146:Immunoglobulin lambda-Chains; D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin; D011993:Recombinant Fusion Proteins