Peripheral blood T cell expansions in patients with Behc¸et's disease

Behc¸et's disease (BD) is a chronic multisystemic inflammatory disorder characterized mainly by recurrent oral and genital aphthous ulcerations and uveitis. Etiology and pathogenesis of BD remain unknown. T cell receptor (TCR) Vα/Vβ gene product expression as well as Jβ gene segment expression in peripheral blood of BD patients were analysed to investigate the possible role of T lymphocytes in the etiopathogenesis of BD. Flow cytometry with 12 TCR V-specific MoAbs was used for TCRV analyses. Jβ gene segment usage by T cell populations expressing certain Vβs was determined by polymerase chain reaction (PCR) technique with Vβ- and Cβ-specific primers, Southern blotting of PCR products, and subsequent hybridization with radiolabelled Jβ gene segment-specific probes. Although 13 of the 23 BD patients exhibited increases in expression of one or more TCR V-gene products, only expansions among the CD4⁺ T cell subset were significantly more frequent in BD patients (7/23) compared with healthy controls (0/15) (P = 0.019). Six out of eight cases followed for up to 20 months had at least one expansion correlated with disease activity. A strict preference for particular Jβ gene segments implicating clonality was apparent in all analysed T cell expansions and correlated well with disease activity. These results suggest a possible involvement of antigen-specific T lymphocytes in the pathogenesis of BD.