[Analysis of costimulatory molecules (CD28-CTLA-4/B7) expression on chosen mononuclear cells in adolescents with Graves' disease during methimazole therapy].

Abstract

CD28 and CTLA-4 are glycoprotein molecules providing the potent costimulatory signal for T cells activation and proliferation via interactions with their ligands B7/BB1 molecule, present on the surface of Ag-presenting cells (APC). The present study was performed to elucidate the relationship between CTLA-4/CD28 molecules and stimulating (TSAb) or blocking (TBAb) antibodies to the TSH-receptor in Graves' disease. The aim of the study was to estimate the expression of CTLA-4 (cytolitic T lymphocyte associated antigen-4, CD152), CD28, B7.1 (CD80) and CD7.2 (CD86) molecules on peripheral blood cells in patients with Graves' disease (GD) (n=28, mean age 15.4), in patients with nontoxic nodular goiter (NTNG) (n=28, mean age 15.6 years) in comparison with sex- and age-matched healthy control subjects (n=28, mean age 15.9 years). The expression of the costimulatory molecules on mononuclear cells was analyzed by the three-color flow cytometry using a Coulter EPICS XL cytometer. Detection of stimulating and blocking antibodies to the TSH-receptor using JPO9 CHO cells in unfractionated serum was measured by a highly sensitive commercial radioimmunoassay. In untreated Graves' patients we observed a significant increase of CD152+ (p<0.004, p<0.004, p<0.001) and CD28+ (p<0.02, p<0.02, p<0.02) T lymphocytes in comparison to the non-toxic nodular goiter patients, healthy control subjects and euthyroid Graves' patients. After 2-6 months of methimazole therapy, the percentages of these cells in the peripheral blood of hyperthyroid patients returned to normal values. The analysis of CD3+ T lymphocytes co-expressing CD152 and CD28 antigens on peripheral blood revealed increased percentages of CTLA-4/CD28 positive cells in patients with Graves' disease (p<0.004, p<0.04) compared to the controls and euthyroid Graves' patients, while B7.1 (CD80) and B7.2 (CD86) molecules were detected only in some hyperthyroid patients on activated monocytes. In addition, 75% of children with untreated hyperthyroidism had positive TSAbs, whereas TBAbs were measured in 3 out of 7 TSAb negative patients with Graves' disease. In untreated Graves' patients a correlation between percentage of CD152+ T cells and serum level of stimulating and blocking antibodies to the TSH-receptor was found, while no such correlation was detected in relation to CD28+ T cells. We conclude that the changes of the expression of costimulatory molecules on peripheral blood mononuclear cells could be an important marker of activity of an autoimmune process in children and adolescents with Graves' disease and that their levels are modulated by thyroestatic treatment.