INTRATHYROIDAL LYMPHOCYTE SUBSETS, INCLUDING UNUSUAL CD4+ CD8+ CELLS AND CD3(LO)TCR-ALPHA-BETA(LO)/-CD4-CD8- CELLS, IN AUTOIMMUNE THYROID-DISEASE

Intrathyroidal lymphocyte subsets were analysed in 13 euthyroid patients with autoimmune thyroid disease by two-colour flow cytometry and compared with subsets in peripheral blood. In both Graves' and Hashimoto's diseases, proportions of intrathyroidal CD5- B cells were higher than in peripheral blood. The numbers of such cells were correlated with serum levels of anti-thyroid microsomal antibodies. Proportions of T cells bearing alphabeta chains of T cell receptors (TCRalphabeta+T; Talphabeta) and CD16+CD57+ natural killer (NK) cells were lower in the thyroid, but proportions of CD3(hi)TCRalphabeta-TCRgammadelta+ (Tgammadelta) cells were not different. Proportions of CD4+Leu-8- helper T cells and CD4+CD57+ germinal centre T cells were higher and proportions of CD4+Leu-8+ suppressor-inducer T cells and CD8+CD57+ or CD8+CD11b+ suppressor T cells were lower than in the blood in both diseases. Proportions of CD5+ B cells were high in Graves' disease, and proportions of CD8+CD11b - cytotoxic T cells were high in Hashimoto's disease. Unexpectedly, CD4+CD8+ cells and CD3(lo)TCRalphabeta(lo)/-CD4-CD8- cells were present in thyroid tissues of both diseases. These findings suggest that: (i) an imbalance in the numbers of regulatory T cells and of NK cells that had appeared in the thyroid resulted in the proliferation of CD5- B cells, which were related to thyroid autoantibody production; (ii) CD5+ B cells and cytotoxic T cells are important for the different pathological features in Graves' and Hashimoto's diseases, respectively; and (iii) intrathyroidal CD4+CD8+ cells and CD3(lo)TCRalphabeta(lo)/-CD4-CD8- cells may be related to the pathogenesis of autoimmune thyroid disease.