Background
The shared epitope (SE) helps the development of rheumatoid arthritis (RA) by an unknown mechanism. The Epstein–Barr virus (EBV) glycoprotein gp110, a major target in the immune control of EBV replication, contains a copy of the SE. We previously showed that frequencies of T-cell precursors specific to EBV gp110 are influenced by HLA-DR polymorphism and that RA patients have low frequencies of T cells specific for EBV gp110.
Objective
To determine the frequency of T cells (limiting dilution analysis) specific for EBV gp110 and a control antigen (Escherichia coli protein extract) in the synovial fluid of patients with RA or various forms of arthritis.
Methods
Nine RA patients (ACR 1987 criteria; mean age 61.1 ± 7.3 years) and 10 controls with inflammatory rheumatic diseases (mean age 42.5 ± 17.4 years) were studied. For RA patients, the frequency of both peripheral blood and synovial T cells specific for EBV gp110 was evaluated.
Results
In the synovial fluid, the frequency of T cells specific for EBV gp110 was significantly higher in RA than in non-RA patients (mean ± SD 2.5 ± 1.6 × 10-6 vs 0.7 ± 0.9 × 10-6; P = 0.02) (no difference for the control antigen: 1.9 ± 3.3 × 10-6 vs 2.1 ± 2.0 × 10-6; P = 0.3). In RA patients, the frequency of T cells proliferating to gp110 was higher in the synovial fluid than in peripheral blood, but without achieving statistical significance (2.5 ± 1.6 × 10-6 vs 2.0 ± 1.8 × 10-6; P = 0.7) (no difference for the control antigen).
Conclusion
A high frequency of T cells specific for EBV gp110 can be detected in the synovial fluid of RA patients, providing further support for the argument that EBV is involved in RA pathogenesis.