Since the CTLA-4 molecule expressed on activated T lymphocytes has recently been suggested to be an important negative regulator in autoimmune diseases, this study was undertaken to investigate the expression and function of CTLA-4 on synovial T cells from patients with rheumatoid arthritis. CTLA-4-expressing T cells were detected using a dual fluorescence flow cytometric method. Only a small percentage of peripheral blood T cells from patients with rheumatoid arthritis had detectable surface CTLA-4 expression (mean ± SD, 1.89 ± 1.92%). However, the levels of CTLA-4- positive T Cells was increased significantly in rheumatoid synovial fluids (5.44 ± 4.96%) and synovial membranes (28.76 ± 14.30%). To explore the role of CTLA-4 molecule in the inflammation of rheumatoid joints, CTLA-4 was blocked with anti-CTLA-4 antibody to assess its effects on the production of tumour necrosis factor α and interleukin 1β in synovial fluid mononuclear cell culture. The addition of anti-CTLA-4 antibody enhanced the production of tumour necrosis factor α and interleukin 1β in a dose-dependent manner. The data suggest that the expression of CTLA-4 plays a downregulatory role in rheumatoid articular inflammation. We thus concluded that CTLA-4 was up- regulated on synovial T cells from patients with RA, and the increased CTLA- 4 expression might exert a down-regulation effect on tumour necrosis factor α and interleukin 1β production.
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