Class II antigens in Hashimoto thyroiditis. II. Expression of HLA-DR on infiltrating mononuclear cells in peripolesis.

Surgical specimens from patients with Hashimoto thyroiditis (HT) or colloid goiter (CG) were analyzed using an immunofluorescence double staining technique to characterize the infiltrating mononuclear cells (MNC) and to determine the possible expression of HLA-DR antigens by these cells. In HT the majority of infiltrating MNC were T cells. In the interstitium T cells with helper/inducer phenotype (Leu 3a+) were more abundant than those with suppressor/cytotoxic phenotype (OKT8+) and approximately 10-25% of all T cells expressed HLA-DR. Among the cells in peripolesis [i.e., protruding between thyroid epithelial cells (TEC)] OKT8+ cells were observed more frequently than Leu 3a+ cells, expression of DR antigens being 7 and 12%, respectively. The occurrence of Leu 3a+ cells in peripolesis is in marked contrast to the findings in colloid goiter where the intraepithelial population of MNC is almost exclusively composed of OKT8+ cells. The various ways in which the peripoletic Leu 3a+ cells could contribute to the special pathogenesis of HT are discussed.