CD4+ T cells and the Th1/Th2 imbalance are implicated in the pathogenesis of Graves' ophthalmopathy

Graves' ophthalmopathy (GO) is considered to be an organ-specific autoimmune disease. However, the pathogenesis of GO is incompletely understood at the present time. To clarify the immunological differences between newly diagnosed GO and Graves' disease (GD) without ophthalmopathy or healthy controls (HC), we examined T-cell profile and the Th1/Th2 profile cell balance in GO (n=20), GD (n=20) and HC (n=20) using flow cytometry. We also assessed the influence of methimazole on the immunocyte profiles in patients with GO and GD and analyzed the relationship of the immunologic changes with CAS, FT3, FT4, TRAb, TMA and TGA among the three investigated groups. We report in this study that: 1) The percentage of CD4+ T cells and the ratio of CD4+/CD8+ cells were higher, but the population of CD8+ T cells was lower in both GO and GD than those of HC (P<0.05); 2) The percentage of CD8−/IFNγ+ T cells (Th1) and the ratio of CD8−/IFNγ+ to CD8−/IL-4+ T cells (Th1/Th2) in GO were considerably higher as compared to those in GD and HC (P<0.05). On the contrary, the population of Th1 cells, as well as the ratio of Th1/Th2 cells, was lower in GD than that of GO and HC (P<0.05); 3) There were no significant differences in T-cell profile and the Th1/Th2 cell balance in either GO or GD patients before and after methimazole treatment; 4) There was a positive correlation of Th1 cell percentage and the Th1/Th2 cell ratio with the clinical activity score (CAS) in GO (P<0.05), whereas CAS in GO had no correlation with the T-cell profile, the percentage of Th2 cells, and TRAb (P>0.05); 5) T-cell subset and the ratio of Th1/Th2 cells did not correlate significantly with FT3, FT4, TRAb, TMA, or TGA in GO and GD (P>0.05). Finally, 6) there were no statistical differences in TRAb, TMA, and TGA between early GO and GD without ophthalmopathy (P>0.05). Collectively, these results indicate that the balance of Th1/Th2 in GO shifts to Th1 dominance and that the cellular immune responses mediated by the Th1-type CD4+ cells might play a dominant role in the pathogenesis of GO, and thus suggest that the Th1 cell percentage and the ratio of Th1/Th2 cell subsets may be potentially utilized as clinical parameters for disease activity, for monitoring the effectiveness of immunosuppressive treatment, or for developing immunospecific forms of therapy for Graves' ophthalmopathy.