ANALYSIS OF IMMUNOGLOBULIN G-KAPPA ANTITHYROID PEROXIDASE ANTIBODIES FROM DIFFERENT TISSUES IN HASHIMOTOS-THYROIDITIS

Antibodies (Ab) to thyroid peroxidase (TPO) are common in patients wit h autoimmune thyroid disease and may play a role in disease pathogenes is. We have prepared immunoglobulin G kappa(IgG kappa) and IgG lambda phage display combinatorial libraries from the cervical (thyroid-drain ing) lymph nodes of 2 Hashimoto's thyroiditis patients and from the th yroid of 1 patient. After selection with purified recombinant human TP O, up to 10 high affinity IgG kappa clones from each tissue source wer e analyzed further. No IgG lambda Fab were detected in the patient wit h the highest TPO Ab titer. Sequence analysis of the clones showed res tricted heavy and light chain usage, similar to that in previously pub lished TPO-reactive Fabs. This was despite the substantially larger si zes of the initial libraries, the use of lymph node tissue to generate libraries, and the analysis of the repertoire in patients with Hashim oto's thyroiditis rather than Graves' disease. There was overall simil arity in sequences obtained from lymph node and thyroid libraries, wit h higher levels of somatic hypermutation in the former. The Fab inhibi ted binding of serum TPO Ab from five patients by 55-95%. These data t ogether with those from previous reports indicate that although there is no unique Ab gene usage, there is the recurrent presence of certain variable regions in the high affinity TPO Ab response.