Diversity of γδ T cells in patients with Behcet's disease is indicative of polyclonal activation

Objective: Behcet's disease (BD) is a multisystemic disease, with vasculitic lesions in the oral and genital mucosa, eyes, joints, skin and brain. We have previously found that γδ T cells are increased in peripheral blood of BD patients. The aim of this study was to investigate the extent of γδ T cells in oral biopsies from BD patients with special emphasis on the restriction of Vγ and Vδ usage.Patients and methods: Expression of Vγ and Vδ chains on peripheral blood γδ T cells from 31 BD patients and 19 healthy controls was analysed by flow cytometry and the expression of Vγ and Vδ chains in nine ulcerated and eight non‐ulcerated oral mucosa from BD patients and non‐ulcerated oral mucosa from three healthy controls was analysed by immunohistochemistry.Results: Vγ9 and Vδ2 were the predominant chains expressed in peripheral blood of BD patients, although other Vγ and Vδ chains were also expressed. The presence of γδ T cells was only observed in the ulcerated oral mucosa but not in the non‐ulcerated mucosa from the BD patients, and not in the non‐ulcerated mucosa from the healthy controls. These γδ T cells showed no preferential expression of any of the Vγ or Vδ chains.Conclusion: These data suggest a polyclonal rather than oligoclonal activation of the γδ T cells. This may indicate that during repeated inflammation of the oral mucosa, the γδ T cells are responding to a wide variety of antigenic stimuli with consequent expansion of γδ T cells expressing various Vγ and Vδ chains and that different antigenic stimuli or responses may be responsible for the clinical heterogeneity of the disease.