CLONING AND CHARACTERIZATION OF TPO AUTOANTIBODIES USING COMBINATORIAL PHAGE DISPLAY LIBRARIES

Thyroid lymphocyte RNA from a Hashimoto patient with high serum levels of autoantibodies to thyroid peroxidase (TPO) was used to construct a phage display antibody library in the phagemid vector pComb3. The lib rary (100,000cfu) encoded IgG1 heavy chains together with kappa light chains. Selection of the phages displaying TPO antibody on TPO-coated ELISA plates yielded a phage population enriched for surface expressio n of TPO antibody Fabs. 3 different Fabs specific for TPO were subsequ ently isolated with affinities in the region of 10(9) molar-1. 2 of th e Fabs recognised the same, or closely related, epitopes on TPO wherea s the third Fab recognised a different epitope. These 2 epitopes were recognised by TPO autoantibodies in the serum of the lymphocyte donor and a series of 10 patient sera. Available sequence data showed that s everal non-self antibodies and non-thyroid autoantibodies use the same V kappa and V(H) germline genes as TPO autoantibodies. There appeared to be no clear relationship between gene sequence or gene family usag e by TPO autoantibodies of the same or similar epitope specificity.