Immunohistochemical characterization of intrathyroid lymphocytes in Graves' disease. Interstitial and intraepithelial populations.

The phenotypic cell surface markers of the lymphocytes present in thyroid tissue from four patients with Graves' disease were quantitatively analyzed using the avidin-biotin immunoperoxidase technique. As control specimens, normal perinodular tissues from three patients who had benign thyroid nodules resected were also studied. In contrast to normal thyroid tissue, which contained very few T cells and no B cells, thyroid tissue of all four patients with Graves' disease contained a lymphocytic infiltrate, and this could be divided into two populations of lymphocytes. The first population was located in the follicular epithelium and expressed a cytotoxic-suppressor T cell marker (Leu2a). On the average, these cells were 4.2 times as numerous in Graves' tissues as in normal tissues (p less than 0.05). Most of these cells did not express Leu1, a pan-T cell marker. The second population was found in the interstitial tissues, often within lymphoid aggregates, and 70 to 83 percent of the cells expressed Leu1. The majority of these cells expressed a helper-inducer T cell marker, Leu3a; Leu3a/Leu2a ratios within aggregates ranged from 1.9 to 2.1. The number of B cells present was small, ranging from 5.8 to 12.1 percent of the interstitial lymphocytes. These findings are consistent with the involvement of both helper-inducer and suppressor-cytotoxic T cells in a localized autoimmune reaction directed, at least in part, against the thyroid follicular epithelial cells.