To test this hypothesis, the presence of EBV episomes in ACPA-expressing B cells was analyzed.<h4>Methods</h4>ACPA-expressing B cells derived from peripheral blood (PB) of seven EBV-seropositive RA patients, and synovial fluid (SF) of one additional EBV-seropositive RA patient, were isolated by flow cytometry. This evidence concerns the gene PRTN3 and rheumatoid arthritis.