[B-cell, T-cell surface phenotypes and epitopes in autoimmune thyroid diseases]

Autoimmune thyroid diseases (AITD) are categorized as organ specific autoimmune diseases, including Graves' disease (GD), Hashimoto's thyroiditis and idiopathic myxoedema. In this article, B-, T-cell surface phenotypes and epitopes in AITD were reviewed. It has been reported that the proportion and absolute number of B and T lymphocyte subpopulation or CD4/8 ratio in peripheral blood from AITD was not different from normal subjects. Those of CD5+ B cells and gamma delta T cells known as autoreactive clones were, however, increased in peripheral blood from GD. In the thyroid tissue of AITD, B-cells with activated markers were predominantly infiltrated rather than T-cells. The CD4/8 ratio and the proportion of CD8+CD11b+ T (suppressor T) cells was decreased in contrast to the increase of CD8+CD11b- T (cytotoxic T) cells. The CD4+4B4+ T (helper/inducer) cells were more predominant than CD4+2H4+ T (suppressor/inducer) cells in thyroid tissue from GD. These abnormality might cause the cell destruction and the enhanced autoantibody production in the tissue of AITD. Thyroglobulin, thyroid peroxidase and thyroid stimulating hormone receptor are known as major autoantigens in AITD. Recently, B-cell and T-cell epitopes on these autoantigen molecules have been defined, using monoclonal antibodies, proteolytic or synthetic peptides with molecular gene engineering. These epitope analysis would be contributed to the autoimmune tolerance in AITD.