CONTEXT:

Surface HLA-DR antigen is usually only expressed by antigen-presenting cells (APC). In autoimmune thyroid disease, follicle cells function as APC, thus expressing HLA-DR. However, non-autoimmune thyroid diseases may also express surface class II antigens.

OBJECTIVE:

To evaluate the presence and pattern of HLA class II expression in autoimmune and non-autoimmune thyroid disorders.

DESIGN:

Retrospective: histopathological and immunohistochemical analysis.

LOCATION:

Referral center, university hospital.

SAMPLE:

Ten histologically normal thyroids, 11 GravesÆ disease, 7 HashimotoÆs thyroiditis, 10 atoxic multinodular goiter and 3 toxic adenomas were analyzed by immunohistochemistry, using a monoclonal antibody anti-HLA-DR.

MAIN MEASUREMENTS:

The presence of these antigens in thyroid follicular cells and their relation to inflammatory infiltrate was evaluated. The pattern of HLA-DR expression in thyroid follicular cells was analyzed: membrane, cytoplasmic or both.

RESULTS:

Although HLA-DR antigens were sparsely present in one of the 8 normal thyroids, in 6 of the 9 atoxic multinodular goiter and in 2 of the 3 toxic adenomas a net positivity could be seen in large areas. In all 5 HashimotoÆs thyroiditis and in 7 of the 10 GravesÆ disease cases. This expression occurred in follicle cells either in contact with inflammatory cells or not. In non-autoimmune thyroid disease, HLA-DR positivity was essentially cytoplasmic, whereas in GravesÆ disease and Hashimoto thyroiditis it was mainly in cell membranes.

CONCLUSIONS:

It is suggested that the HLA class II expression on the surface of follicle cells could be related to auto-antigen presentation to the immune system by these cells, leading to inflammation