OBJECTIVES Behçet's disease (BD) is a helper T cell-mediated autoimmune disease characterised by recurrent orogenital ulcers, uveitis and skin lesions. The helper T cells are divided into Th1, Th2 and Th17 cells according to the pattern of cytokine secretion. Th1 and Th17 cells can contribute to the development of the disease with their respective proinflammatory cytokines, IFN-γ and IL-17. In this study, we investigated the relative role of Th17, Th1 and Th2 cells in BD.

METHODS Peripheral blood mononuclear cells were isolated from 30 patients with BD, for whom the detailed clinical manifestations and medication history were investigated and recorded. Surface markers and intracellular levels of IL-17, IFN-γ and IL-4 in isolated CD4+ T cells were measured using flow-cytometry from these patients and from two control groups, 34 rheumatoid arthritis patients and 24 healthy blood donors to analyse the relationship of Th1, Th17 and Th2 cells in BD.

RESULTS The ratio of Th17/Th1 cells was significantly increased in BD compared to healthy controls (0.16±0.09 vs. 0.10±0.04, p=0.012), while there was no difference in the ratios of Th1/Th2 or Th17/Th2 cells. Th17/Th1 ratio was elevated in BD patients with uveitis or folliculitis compared to those without it (0.21±0.10 vs. 0.13±0.06, p=0.045 for uveitis; 0.18±0.10 vs. 0.12±0.05, p=0.036 for folliculitis).

CONCLUSIONS Our results confirm that TH17 cells are instrumental in Behçet's uveitis and folliculitis. Furthermore, our findings suggest that the role of Th17 cells should be interpreted in the context of their ratio to Th1 cells.