Immunoreactivity of multiple molecular forms of human thyroglobulin

Area of Science:

• Endocrinology
• Immunology
• Biochemistry

Background:

• Human thyroglobulin (Tg) is a key protein in thyroid hormone synthesis.
• Alterations in Tg structure and antigenicity are observed in autoimmune thyroid diseases like Graves' disease.

Purpose of the Study:

• To purify and characterize human thyroglobulin (Tg) from normal individuals and Graves' disease patients.
• To compare the protein content, iodine content, and immunological properties of Tg from these two groups.
• To investigate the role of iodine in Tg antigenicity using monoclonal antibodies (mAbs).

Main Methods:

• Purification of human Tg using gel filtration (Sephacryl S-400) and ion-exchange (DEAE) column chromatography.
• Characterization of isolated Tg protein peaks for protein and iodine content.
• Assessment of immunological properties via reactivity with polyclonal and monoclonal antibodies (mAbs).

Main Results:

• Five distinct Tg protein peaks were isolated from the DEAE column.
• Normal and Graves' Tg exhibited differences in the relative protein content of these peaks, with Graves' Tg predominantly in peak 1.
• Graves' Tg showed significantly higher immunoreactivity with patient sera and most mAbs compared to normal Tg, particularly in peak 1.
• One mAb (42C3) demonstrated iodine-dependent immunoreactivity, paralleling Tg iodine content.

Conclusions:

• Graves' disease is associated with altered human thyroglobulin (Tg) protein profiles and enhanced immunoreactivity.
• Specific monoclonal antibodies (mAbs) can distinguish between normal and Graves' Tg.
• A novel mAb (42C3) highlights the critical role of iodine in Tg antigenicity and may be a tool for its evaluation.