Endocrine Abstracts

Introduction: Radioactive iodine (RAI) for Graves’ disease (GD) was reported to have specific immune effects. The ability of T and B lymphocytes to cooperatively interaction during the immune response may be impaired in GD patients eligible for RAI therapy. We aimed at investigating cellular subsets involved in functional activity of adaptive immunity cellsone month after RAI therapy in patients with GD.

Materials and methods: Thirty-six women with GD, mean age 42.13±15.35, were included in this study. All patients treated with thiamazole for at 12 months (9 – 14) before RAI therapy. Thiamazole was withdrawal 14 days before RAI therapy. All patients had a fixed 400-700 MBq ¹³¹I dose orally. Fifty-six healthy subjects were also studied. The study of the phenotype of T- and B-lymphocytes was carried out by flow cytometry using direct immunofluorescence of whole peripheral blood and monoclonal antibodies labeled with FITC (fluorescein isothiocyanate), PE (phycoerythrin), ECD (phycoerythrin-Texas Red-X), PC5 (phycoerythrin-cyanin 5), PC7 (phycoerythrin-cyanin 7), AA700 (alexa fluor 700) and AA750 (alexa fluor 750) in the following panels: CD8-FITC/CD127-PE/CD25-PC5/CD4-PC7/CD3-AA700/CD45-AA750 и CD5-FITC/CD23-PE/CD19-ECD/CD45-PC5/CD27-PC7. Serum measurement of TSH, fT4, fT3 and TRAb were performed by ELISA and enzyme immunoassay.

Results: The thyroid state of GD patients before RAI treatment corresponded to subclinical hyperthyroidism with a high level of serum TRAb (Ме=28,01 mU/l (Q_0,25=2,81; Q_0,75=35,71, р<0,001)). An increase in the percentage of CD3⁺CD25⁺ CD3⁺CD4⁺ CD3⁺CD4⁺CD25⁺ and CD3 ⁺CD8⁺CD25⁺ cells but with a decrease in the amount of CD3⁺CD8⁺ lymphocytes relative to the control was found in GD patients before RAI therapy. All patients treated with RAI were euthyroid, while the content of TRAb remained almost at the initial level. One month after RAI therapy in GD patients we observed decreased the percentage of cells with phenotypes CD3⁺CD25⁺ CD3⁺CD4⁺CD25⁺ and CD3⁺CD8⁺CD25⁺ and an increase number of CD3⁺CD4⁺CD127^LowCD25High lymphocytes. Also, we detected changes in the phenotypic composition of blood B lymphocytes of GD patients before ¹³¹I treatment: a decrease the percentage of CD19⁺ cells and an increase the relative number of CD19⁺CD27⁺CD23⁺ lymphocytes. One month after RAI therapy we revealed decreased percentage of CD19⁺CD5⁺CD23⁺ lymphocytes and increased relative to the initial values the levels of CD19⁺CD27⁻ and CD19⁺CD5⁻ cells.

Conclusion: One month after RAI therapy in GD patients changes in the phenotype of T and B lymphocytes in the blood reflect a tendency towards a decrease in the functional activity of adaptive immunity cells which can also be realized in the inhibition of autoimmune processes.