An intrathyroidal T-cell clone specifically cytotoxic for human thyroid cells.

We have isolated the first human T-cell clone (IM8) that is specifically cytotoxic to autologous human thyroid cells. In order to obtain primary immunologically reactive cells in patients with autoimmune thyroiditis, we cloned, by limiting dilution, in vivo activated intrathyroidal T lymphocytes against thyroid antigens. Clone IM8 expresses CD8 surface antigen, has no activity against autologous or allogeneic mitogen-stimulated lymphoblast cells or allogeneic thyroid cells, and does not lyse K562 cells, implying a lack of natural killer (NK) activity. This observation suggests a role for IM8-like clones in the immunopathology of human autoimmune thyroid disease.