[High expression of ICOS on CD4⁺ T cells and ICOSL on CD19⁺ B cells in peripheral blood and its positive correlation with TRAb in Graves' disease].

Objective To detect the expression of inducible co-stimulator and inducible co-stimulator ligand (ICOS/ICOSL) on peripheral lymphocytes in patients with Graves' disease (GD) and its clinical significance. Methods A total of 105 untreated GD patients and 67 healthy controls were enrolled in our study. 19 GD patients treated with anti-thyroid drugs were followed up in the outpatient department until TRAb were negative. The peripheral blood mononuclear cells (PBMCs) were separated and analyzed with PCR. ICOS expression on CD4⁺/CD8⁺ T cells and ICOSL expression on CD19⁺ B cells were detected by flow cytometry. The correlations between the expression of ICOS/ICOSL with thyroid parameters and TRAb were analyzed. Results The expression of both ICOS and ICOSL mRNA in PBMCs of the untreated GD patients were significantly higher than those in the healthy controls. Compared with healthy controls, ICOS expression on CD4⁺ T cells and ICOSL expression on CD19⁺ B cells were up-regulated significantly in the GD patients. Correlation analysis showed that ICOS expression on CD4⁺ T cells was positively correlated with the level of free triiodothyronine (FT3) in the GD patients. In the group of GD patients with high TRAb titers in serum, ICOSL expression on CD19⁺ B cells notably increased as compared with that in the patients with low TRAb. ICOS expression on CD4⁺ T cells and ICOSL expression on CD19⁺ B cells were recovered in the GD patients with negative TRAb. Conclusion The expression of ICOS on the surface of CD4⁺ T cells and ICOSL on CD19⁺ B cells in peripheral blood of patients with Graves's disease are significantly increased.With the decrease of TRAb level, the expression levels of ICOS on the surface of CD4⁺ T cells and ICOSL on CD19⁺ B cells are restored.

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