IMMUNOREACTIVITY OF MULTIPLE MOLECULAR-FORMS OF HUMAN THYROGLOBULIN

Human thyroglobulin (Tg) was purified from thyroids of normal individu als and of patients with Graves' disease using gel filtration (Sephacr yl S-400) and ion-exchange (DEAE) column chromatography. We isolated f ive protein peaks of Tg from the DEAE column, using a step gradient, c haracterized them for protein and iodine content, and assessed their i mmunological properties by reactivity to polyclonal and monoclonal ant ibodies (mAbs). Normal and Graves' Tgs differed in the relative protei n content of these five protein peaks from the DEAE column. In the cas e of normal Tg, the majority of Tg was eluted in peak 2 but in the Gra ves' Tg, most of the protein was eluted in peak 1 of this column. The immunoreactivity of these five protein peaks of Tg was studied using 1 1 mouse mAbs prepared against human Tg, sera from patients with autoim mune thyroiditis and polyclonal antibody from a rabbit immunized with human Tg. All of five protein peaks of Tg reacted equally with rabbit antibody. The sera of five thyroiditis patients showed greater binding to peak 1 of Graves' Tg than peak 1 of normal Tg. Similarly, most mAb s showed greater binding to peak 1 of Graves' Tg than the peak 1 of no rmal Tg. Of particular interest was one mAb (42C3) which reacted only with Tgs containing iodine. The immunoreactivity of this mAb parallele d the iodine content of Tg. This mAb might be useful for evaluating th e role of iodine in the antigenicity of human Tg. (C) 1994 Academic Pr ess, Inc.