Expression of intercellular adhesion molecule-1 in thyroid follicular cells in autoimmune, non-autoimmune and neoplastic diseases of the thyroid gland : discordance with HLA

The presence of intercellular adhesion molecule-1 (ICAM-1) on epithelial cells facilitates their recognition by specific T lymphocytes. To assess the possible role of ICAM-1 in the recognition of thyroid follicular cells by T cells in thyroid autoimmune disease, we investigated the expression of ICAM-1 in thyrocytes from thyroid glands affected by Graves' disease, in gland with non-autoimmune pathology and normal glands using immunofluorescence staining on cryostat sections and on dispersed cell preparations. Sequential tissue sections from glands affected by Graves' disease ( n =15), multinodular goitre (MNG, n =26), benign nodules ( n =11), primary carcinomas ( n =12) and control thyroid gland ( n =5) were stained for ICAM-1, HLA class I, HLA class II, CD3 and thyroid peroxidase (TPO). Weak and patchy ICAM-1 expression was found in the thyrocytes of 4/15 (27%) Graves' disease and of 1/26 (4%) multinodular goitre glands. In contrast, ICAM-1 expression was detected in the thyrocytes of 5/11 (45%) benign nodules and of 8/12 (67%) thyroid carcinomas in which it was sometimes strong. Thyrocytes in the five control glands were negative. These results correlated well with flow cytometry data from 23 of these glands which showed that ICAM-1 expression in thyrocytes from Graves' patients was, when present, ‘dull’, while in some malignant thyrocytes it was ‘bright’. In preparations of thyrocytes from Graves' disease glands we found a striking discordance between the high levels of expression of HLA class I and HLA class II and the low expression of ICAM-1. This is surprising since in vitro the expression of these three molecules is equally induced by IFN-γ and TNF-α. These results suggest that additional factors are involved in the induction of the inappropriate HLA class II expression observed in the thyrocytes of glands affected by Graves' disease.