The effect of sulphydryl reagents on the human thyroid microsomal antigen

Abstract. Evidence has been accumulated that human thyroid microsomal/microvillar autoantigen (M) is expressed both in the cytoplasm and on the surface of thyroid follicular cells. The availability of this autoantigen to the immune system, possibly associated with abnormally expressed HLA-DR antigens may be relevant both to the triggering and to maintenance of thyroid autoimmune reactions. Preliminary biochemical characterization of M suggested that it was a glycoprotein with a mol. wt. of about 100–110 kD. recent studies carried out in our laboratories taking advantage of monoclonal antibodies provided evidence that the structure presently referred as M-Ag is represented by thyroid peroxidase (TPO). The identity between TPO and M is further supported by four-layer immunofluorescence analysis showing a complete overlap of the two antigens both in the surface and in the cytoplasm of thyroid cells and by the observation that the expression of M and TPO is similarly modulated by TSH, possibly through a cAMP-dependent mechanism.

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Antibodies to membrane antigens in autoimmune thyroid disease

Acta Endocrinologica ◽

10.1530/acta.0.1160013 ◽

1987 ◽

Vol 116 (1) ◽

pp. 13-20 ◽

Cited By ~ 6

Author(s):

J. Furmaniak ◽

J. Bradbury ◽

B. Rees Smith

Keyword(s):

Solid Phase ◽

Protein A ◽

Human Thyroid ◽

Intermediate Filament Protein ◽

Autoimmune Thyroid Diseases ◽

Autoimmune Thyroid ◽

Microsomal Antibody ◽

Membrane Antigens ◽

Solid Phase Assay ◽

Microsomal Antigen

Abstract. The possibility that sera from patients with autoimmune thyroid diseases contain autoantibodies to thyroid membrane proteins distinct from microsomal antigen and the TSH receptor has been investigated using (a) solid phase assay system based on human thyroid membranes and 125I-labelled protein A and (b) immunoprecipitation of detergent solubilized 125I-labelled thyroid membranes followed by gel electrophoresis and autoradiography. In the solid phase assay binding to membranes showed a highly significant correlation with binding to microsomes (r = 0.82; P < 0.001; N = 82) indicating that the interaction between the serum and the membranes was due principally to microsomal antibody binding to microsomal antigen contaminating the membrane preparations. However, there were some discrepancies suggesting that an additional antigen-antibody system was involved. This possibility was then investigated using immunoprecipitation of 125I-labelled thyroid membranes. A labelled protein with mol wt 54 K was specifically immunoprecipitated (relative to normal pool serum) by 3 out of 4 sera from patients with Graves' disease who showed high binding to thyroid membranes. A further 4 sera from such patients with low membrane binding affinity failed to immunoprecipitate the 54 K protein. Sera from some patients with Hashimoto's disease and some patients with rheumatoid arthritis and one patient with Addison's disease also immunoprecipitated the 54 K protein from solubilized thyroid membranes. These studies suggested that antibodies interacting with the 54 K protein contributed to the discrepancies between thyroid membrane and microsome binding. However, the 54 K protein was also immunoprecipitated from detergent solubilized membranes prepared from human placenta, skeletal muscle and adrenal tissue. Immunoprecipitation studies with antisera to cytoskeleton proteins suggested that the 54 K band was the intermediate filament protein desmin. Consequently, thyroid specific antibody-antigen systems distinct from those involving microsomal antibody (or thyroglobulin antibody) could not be detected in thyroid membranes by immunoprecipitation.

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