Recognition by recombinant autoimmune thyroid disease-derived Fab fragments of a dominant conformational epitope on human thyroid peroxidase.
To characterize the nature of thyroid peroxidase (TPO) autoantibodies present in the sera of patients with autoimmune thyroid disease, we cloned three IgG1/kappa Fab fragments which bind 125I-TPO. This was accomplished by the molecular cloning and expression in bacteria of IgG gene fragments from B cells infiltrating the thyroid of a patient with Graves' disease. The three Fab fragments (SP2, SP4, and SP5) are coded for by a common heavy chain (VH1, D, JH3) and three related, but different, light chains (VK1, JK2). The SP Fab fragments bind specifically to TPO with high affinities (6 x 10(-11)-2 x 10(-10) M) comparable to those of serum TPO autoantibodies. TPO autoantibodies represented by the SP Fab fragments are present in all 11 patients studied, constitute a high proportion (36-72%) of serum TPO autoantibodies in individual patients and interact with a conformational epitope on TPO.
Portolano
S
S
Thyroid Molecular Biology Unit, Veterans' Administration Medical Center, San Francisco, California 94121.
Chazenbalk
G D
GD
Seto
P
P
Hutchison
J S
JS
Rapoport
B
B
McLachlan
S M
SM
D000595:Amino Acid Sequence; D001323:Autoantibodies / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology*; D001483:Base Sequence; D000939:Epitopes / Q000032:analysis*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology*; D007453:Iodide Peroxidase / Q000276:immunology*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000276:immunology; D013959:Thyroid Diseases / Q000276:immunology*
D001323:Autoantibodies; D000939:Epitopes; D007140:Immunoglobulin Fab Fragments; D011994:Recombinant Proteins; D007453:Iodide Peroxidase