FOLLICULAR THYROID-CELLS OF AUTOIMMUNE-THYROIDITIS MAY COEXPRESS ICAM-1 (CD54) AND ITS NATURAL LIGAND LFA-1 (CD11A CD18)/

The leukocyte functional associated antigen-1 (LFA-1)-intercellular ad hesion molecule-1 (CD11a-CD18/CD54) intercellular adhesion system play s a crucial role in several immunologic phenomena, including adhesion between lymphocytes and epithelial cells. In previous studies evidence for CD54 expression on thyroid follicular cells in Hashimoto's thyroi ditis was provided. In this study we evaluated the possible expression of CD11a and CD18 antigens on thyrocytes of patients with Hashimoto's thyroiditis and on thyrocytes of patients with Graves' disease and si mple goiter as controls; we used both alkaline phosphatase immunostain ing and indirect immunofluorescence on cryostatic tissue sections. The results showed that LFA-1 (both CD11a and CD18) positivity on thyroid follicles may occur in glands of patients with Hashimoto's disease, w ith a pattern very similar to that of CD54: this was observed in five of seven specimens. Conversely, no positivity was observed in tissues from patients with Graves' disease or goiter: notably, isolated follic ular cells from Graves' goiter tissues are induced in culture to expre ss CD54, but not LFA-1. Using double-staining techniques, we were able to show that in specimens from patients with Hashimoto's disease, the same follicular structures coexpressed LFA-1 and CD54. Such a coexpre ssion of the two ligands further emphasizes the possible role of this adhesion system in the pathogenesis of epithelial damage, through bidi rectional interactions between thyroid epithelial cells and infiltrati ng LFA-1 or CD54-positive mononuclear cells.