Relationship Between Sjögren's Syndrome (SS) and Epstein-Barr Virus (EBV): Antibody to EBV, EBV Excretion from the Oropharynx and EBV Secretion from the Spontaneously Established SS B Cell Lines

Sjögren's syndrome (SS), an autoimmune exocrinopathy, is characterized by polyclonal B cell activation and association of monoclonal B cell lymphoma. We therefore studied possible involvement of EBV in the pathogenesis of SS. EBV is known to be a polyclonal B cell activator and an oncogenic virus. The titer of serum antibody of IgG class against viral capsid antigen (VCA) was significantly elevated in SS sera. Serum anti-VCA antibody of IgM class was also significantly increased in titer in SS. Ten out of 37 SS sera had titers of both IgG and IgM anti-VCA antibodies suggesting reactivation of EBV in vivo. These cases had significantly enhanced level of serum IgG compared to SS patients without reactivation. Excretion of EBV from the oropharynx was frequently observed in SS (86%) compared to normal controls (33%). SS patients with increased anti-VCA antibody in the sera tended to be EBV excretors. Furthermore, we have successfully established B cell lines from the peripheral blood of SS patients but not from normal controls, when peripheral blood mononuclear cells were cultured without stimulation. These cell lines not only expressed EBV nuclear antigen (EBNA) but also excreted large amount of EBV in the culture. These data might suggest possible involvement of EBV in the pathogenesis of SS.