Blood and thyroid-infiltrating lymphocyte subclasses in juvenile autoimmune thyroiditis.

We have studied the distribution of T and B lymphocytes in the blood and in the thyroid lymphocytic infiltrates (obtained by fine needle aspiration biopsy) in sixteen patients with juvenile autoimmune thyroiditis (JAIT). The same cell populations were also tested for cell-mediated immunity (CMI) to thyroid antigen in the leucocyte migration test (LMT). The relative and absolute numbers of blood T lymphocytes were normal (71-76%), as were the numbers of blood B lymphocytes (19%). The thyroid infiltrate contained 48% B lymphocytes, whereas only 40-44% of the infiltrating lymphocytes were T cells. Half of the JAIT patients showed a positive CMI to thyroid antigen with blood leucocytes, but when thyroid-infiltrating lymphocytes of these patients were tested in the LMT, they were negative. Thus, in contrast to what is generally assumed, we were unable to demonstrate T cell-dominated lymphocytic infiltrates or the accumulation of specifically sensitized T lymphocytes within the thyroid gland in autoimmune thyroiditis.