Expression of various MHC class II molecules and of intracellular adhesion molecule-1 (ICAM-1) on focal clusters of dendritic cells in iodine deficiency goitres.

Thyroid sections from 18 consecutive euthyroid patients undergoing surgery for iodine deficiency goitre were investigated by means of immunohistochemistry and immunofluorescence, evaluating the expression of MHC class II antigens (HLA-DR, -DP, -DQ, and RFD1) and intercellular adhesion molecule-1 on the formerly described clusters of dendritic cells, as well as on thyrocytes. Eleven of 18 iodine deficiency goitres contained clusters of dendritic cells. These clusters appeared to express only HLA-DR in two cases; in nine of 12 cases they showed a differential expression of class II molecules in the following frequency: HLA-DR > DQ and/or -DP > RFD1. These dendritic cells also were ICAM-1+. In four of 18 iodine deficiency goitres, thyroid epithelial cells showed MHC class II expression in several combinations, but were ICAM-1-. In normal thyroids and in nodular goitres from inhabitants of the endemic area not having an actual iodine deficiency, only sparse clusters of dendritic cells were found; these cells were only HLA-DR+. Follicle lining cells were negative for the MHC class II molecules. In normal thyroids from an area with sufficient iodine supply, no clusters of dendritic cells were seen. The few dendritic cells observed were lying isolated in the interstitium and only positive for HLA-DR and ICAM-1; epithelial cells were negative for the studied markers. These data show clusters of dendritic cells in thyroids of inhabitants of an endemic area. When goitre is accompanied by iodine deficiency at the moment of operation, there appears to be activation of these dendritic cells and of thyroid epithelial cells.