OBJECTIVE: To investigate control of Epstein-Barr virus (EBV) infection in rheumatoid arthritis (RA) by comparing the frequency phenotypes and function of peripheral CD8+ EBV-peptide antigen-specific T cells in patients with RA and healthy longterm carriers of EBV. METHODS: The frequency of interferon-g (IFN-g)-producing HLA-A2 or HLA-B8-restricted EBV-reactive CD8+ T cells in peripheral blood mononuclear cells (PBMC) from 49 RA patients and 26 healthy EBV carriers was evaluated in Elispot assays with 12 lytic/latent peptide epitopes. Direct staining with HLA-peptide tetramers containing 3 of these peptides was performed for comparison. The phenotype and function of these T cells was determined by FACS and cytotoxicity testing. RESULTS: IFN-g production patterns in Elispot assays revealed that EBV-specific CD8+ T cells were directed predominantly against the lytic epitopes A2/GLC and B8/RAK and to a minor extent to all the other lytic and latent epitopes tested, with no significant differences of the frequencies in patients and controls. However, although similar frequencies of CD8+ T cells stained with A2/GLC or B8/RAK tetramers in both groups, the fraction of A2/GLC or B8/RAK-reactive T cells producing IFN-g in response to specific peptide antigen was significantly lower in RA patients than controls. The A2/GLC or B8/RAK tetramer-positive T cells were also substantially enriched in CD28-CD27- T cells of a late-differentiated phenotype in RA patients but not in controls. CONCLUSION: RA patients show clonal expansion of dysfunctional, terminally differentiated CD8+ EBV-specific T cells in their T cell responses to immunodominant lytic peptide EBV epitopes, which could be a sign of specific impairment of virus-host interactions in RA.