SUMMARYBehçet's disease (BD) is a multisystem disorder with oral and genital ulcers, mucocutaneous, ocular, joint, vascular and central nervous system involvement. In this study, the peripheral T cell repertoire was analysed in patients with BD with MoAbs against T cell receptor (TCR) Vb gene products in CD4 þ and CD8 þ T cell compartments, and these were compared with rheumatoid arthritis (RA) patients and healthy controls (HC). In the CD4 þ T cell compartment, oligoclonal TCR Vb expression was observed in 56% of BD (10/18), 71% of RA (5/7) patients and 21% (3/14) of HC. In the CD8 þ T cell group 50% of BD (9/18), 57% of RA patients and 28% of HC (4/14) had an oligoclonal TCR repertoire. An increase of TCR Vb5.1 subset was observed in five BD patients among CD8 þ T cells. Other elevations of TCR Vb subsets were heterogeneously distributed with one to three different Vb subsets. Our results suggest an antigen-driven oligoclonal increase of T cells in BD. There was no overall increase in any Vb group to suggest a superantigen effect. Analysis of the responsible antigens causing the increase in T cell subsets may give insights into the aetiopathogenesis of BD and immunomodulation of these T cells may lead to new treatments.

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