CLONING AND ANALYSIS OF IGC-KAPPA AND IGG-LAMBDA ANTITHYROGLOBULIN AUTOANTIBODIES FROM A PATIENT WITH HASHIMOTOS-THYROIDITIS - EVIDENCE FORIN-VIVO ANTIGEN-DRIVEN REPERTOIRE SELECTION

Antibodies to thyroglobulin (Tg) are commonly found in patients with t he autoimmune thyroid diseases Graves' disease and Hashimoto's thyroid itis as well as in individuals with apparently normal thyroid function . Although it is not clear how Tg Abs are involved in the pathology of the diseases, the study and analysis of these Abs may nevertheless be instructive in allowing the development of an Ab response to an autoi mmune disease-associated self Ag to be followed. We have prepared IgG kappa and lambda phage display combinatorial libraries from the cervic al lymph node of a single Hashimoto's thyroiditis patient with a high anti-Tg titer. These were selected with purified human Tg, and 10 IgG kappa and 9 IgG lambda clones were analyzed further. Sequence analysis of the clones showed a very highly restricted heavy chain usage and a less restricted light chain usage. There was a variable degree of div ergence from germ-line sequence in the light chain sequences, with a c lear relationship between relatively higher affinity of the Fab for hu man Tg and an increased degree of somatic hypermutation. The Tg-select ed Fab did not bind to Tg from other species, to reduced denatured Tg, or to thyroid peroxidase. The Fab inhibited patient serum binding to human Tg by between 39 and 79%. In summary, we have isolated 19 high a ffinity, human Tg-specific Fab and shown that the relative affinity of the Fab is directly related to the pattern of somatic hypermutation.