L-Thyroxine-induced leukopenia in a patient with Hashimoto's disease: involvement of suppressor-cytotoxic T cells.

A study of in vitro reactivity to L-T4, as assessed by peripheral blood lymphocyte transformation, was carried out in a patient with Hashimoto's disease who developed leukopenia during treatment with L-T4. L-T4 stimulated lymphocyte transformation in this patient. The proliferating cells were of T lineage and further typing demonstrated that they bore the OKT8 antigen. Cell-mediated immune reactions mediated by OKT8+T cells might have caused the leukopenia, although other mechanisms involving cytotoxic antibodies or antibody-dependent cell-mediated cytotoxicity cannot be excluded.