Lymphocytes in the structure of non-neoplastic goitre

Mononuclear cells infiltrating the thyroid in various pathological states including those of the autoimmune etiology are common. The role of mononuclear infiltrates in Hashimoto's goiter or Graves-Basedow disease is well understood. The present study was undertaken to analyze the immunophenotype of lymphocytes and the occurrence of antigen presenting cells in Graves-Basedow disease, toxic nodular goiter or simple goiter to compare these disease entities with respect to their role in autoimmunization with thyroid antigens. Ninety-four thyroid specimens obtained from goiter patients undergoing surgery were studied. Cryostat sections were investigated with a panel of antibodies against antigens of lymphocyte differentiation using immunohistochemistry by APAAP. Semiquantitative technique was used to count the cells with positive reactivity in the visual field magnified 400 times under a light microscope. The structure of goiter varying in etiology contained all basic lymphocyte subpopulations and antigen presenting cells. T lymphocytes, especially CD3+, CD4+ cells were predominant, however, the differences did not significantly correlate with any of the above mentioned patient group. There were also the signs of activation of infiltrate cells confirmed by a positive reaction with antibodies against class II MHC antigens. However, the presence of these cells did not correlate significantly with any of the analyzed groups. Furthermore, the expression of HLA class II antigens on epithelial cells of the thyroid was found in all groups, however much more frequently in Graves-Basedow disease and toxic nodular goiter. This indicates a possibility of autoimmunization in the thyroid microenvironment in all study groups and a need to verify the views on the pathogenesis of thyroid diseases so far considered as not related to autoimmunization.