Accumulation of human T lymphotropic virus type I‐infected T cells in the salivary glands of patients with human T lymphotropic virus type I‐associated Sjögren's syndrome

Objective To clarify the involvement of human T lymphotropic virus type I (HTLV‐I) in the pathogenesis of Sjögren's syndrome (SS). Methods In HTLV‐I‐seropositive patients with SS, HTLV‐I proviral DNA in the labial salivary glands (SG) was detected by polymerase chain reaction (PCR) amplification of the extracted cellular DNA, and the localization in the SG was examined by in situ PCR hybridization. Results The cellular DNA extracted from the SG contained full HTLV‐I proviral DNA, which was present in the nucleus of the infiltrating T cells, but not in either the SG epithelial cells or the acinar cells. Furthermore, the viral loads in the SG were ∼8 times to 9 × 103 times higher than those in the peripheral blood mononuclear cells. Conclusion Accumulation of HTLV‐I‐infected T cells in the SG suggests that HTLV‐I likely causes the self‐reactive T cells to proliferate, which, as a result, induces SS.