The effects of radioiodine therapy on peripheral blood lymphocyte subpopulations in patients with Graves' disease. Preliminary report.

BACKGROUND Treatment of Graves' disease patients with radioactive iodide ((131)I) is becoming the standard therapy in an increasing group of cases but can induce alterations in immune response, like increasing levels of thyroid autoantibodies, and, in part, exacerbation of ophthalmopathy. The aim of this study was to assess the changes in peripheral blood (PB) lymphocyte subpopulations after (131)I treatment of patients with Graves' disease. MATERIAL AND METHODS The study was carried out in a group of 30 patients with Graves' disease (23 f; 7 m) 49.5 +/- 10.0 years of age, 26 with different subjective ocular signs like gritty sensation, increased lacrimation, orbital pain, and exophthalmos. PB lymphocyte subsets were analysed by cytofluorometry, serum concentration of TSH and fT4 were evaluated before and 6 weeks after radioiodine treatment. RESULTS After (131)I treatment a significant increase in CD3+, CD4+, CD3+HLA-DR+ and a decrease in CD19+ percentages of lymphocyte subsets were found in comparison with the initial evaluation. No significant changes in percentage of CD8+ and NK (CD3-CD16+ CD56+) cells were observed during this study. A significant increase in TSH and a slight decrease in fT4 concentration concentration took place in the 6th week after (131)I application. The patients without subjective improvement of ocular signs during the therapy initially had a percentage of CD3+, CD8+ lymphocytes which was significantly lower compared with those with regression of ocular signs observed after 131I treatment. CONCLUSIONS The changes in PB lymphocyte subsets caused by (131)I treatment of Graves' disease confirm the involvement of acquired cellular immunity after radiation damage of the thyroid gland. The decreased initial percentage of CD8+ and CD3+ lymphocytes could help make a prediction of ocular symptoms persisting after radioiodine treatment in some patients with ophthalmopathy.