Thyrocyte HLA-DR expression and interferon-gamma production in autoimmune thyroid disease

We examined the expression of HLA-DR antigen induced by mitogen, mitogen-free supernatants from mitogen-stimulated peripheral blood mononuclear cells (PBMC), or autologous and allogeneic PBMC on thyrocytes cultured for 1-2 weeks (precultured) before the addition of the stimulant. Leucoagglutinin (LAG) and concanavalin A, but not lipopolysaccharide induced HLA-DR expression on thyrocytes from normal subjects (NC) and patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT). The degree of DR expression induced by LAG was significantly less in GD than in NC thyrocytes. This response was dependent on contaminating T cells, especially suppressor-cytotoxic T (Ts/c) cells, NK cells, and HLA-DR+ cells, but not helper-inducer T (Th/i) cells or B cells, in the thyrocyte cultures. OKT3 monoclonal antibody, which activates T cells specifically in the presence of monocytes, also induced thyrocyte HLA-DR expression. Furthermore, interferon-gamma (IFN-gamma) was detected in culture supernatants from LAG-stimulated thyrocytes. Anti-IFN-gamma monoclonal antibody eliminated the ability of LAG to induce HLA-DR. Mitogen-free supernatants from mitogen-stimulated PBMC also induced thyrocyte HLA-DR expression, which was inhibited by anti-IFN-gamma. The supernatants of concanavalin A- or LAG-stimulated PBMC from either untreated or recently treated patients with GD or hypothyroid HT induced less thyrocyte DR expression than NC PBMC. Indeed, the levels of IFN-gamma in supernatants from such patients were lower than those in NC, and the correlation between DR expression and IFN-gamma levels was significant. This IFN-gamma production by PBMC required Th/i cells, NK cells, and HLA-DR+ cells. Before the addition of autologous or allogeneic PBMC, only precultured HT thyrocytes expressed HLA-DR, whereas GD and NC thyrocytes did not. The induction or enhancement of DR expression on autologous thyrocytes by direct coculture with PBMC occurred within 8 days in GD and HT, but not in NC. There was a significant correlation between the serum titer of antithyroid microsomal antibodies and the degree of DR expression. Allogeneic normal PBMC also induced DR expression on NC and GD thyrocytes within 8 days, the effect on the latter being more pronounced than with autologous GD PBMC. Thyrocyte HLA-DR expression induced by autologous GD PBMC and allogeneic normal PBMC required monocytes. Th/i, and NK cells and was blocked by anti-IFN-gamma. However, the enhancement of thyrocyte DR expression by autologous HT PBMC did not require monocytes.(ABSTRACT TRUNCATED AT 400 WORDS)