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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.

Oral squamous cell carcinomas (SCC) are often infiltrated by a large number of T lymphocytes. To clarify the nature of the tumour-infiltrating lymphocytes (TIL), we examined T cell receptor (TCR) V alpha and V beta gene usage by TIL and peripheral blood mononuclear cells (PBMC) obtained from 10 patients with oral SCC. We obtained RNA from TIL and PBMC, synthesized complementary DNA, and used the polymerase chain reaction (PCR) method with a panel of primers specific for the V gene segment subfamily (V alpha 1-18/V beta 1-20). We thus found that TIL showed more restricted usage of V beta gene families in contrast to PBMC of the same patients while two unique V beta gene (V beta 6 and V beta 5.2) segment transcripts were overexpressed in the TIL of more than half of the patients. On the other hand, no major difference was observed in the V alpha gene usage between the TIL and PBMC of most patients. To characterize these T cell subpopulations with unique V beta gene segment transcripts further, we sequenced the complementarity-determining region 3 in V beta 6-C beta and V beta 5.2-C beta PCR products derived from TIL and PBMC of two selected patients in each case. Although no usage of the conserved amino acid sequence by TIL was detected, the frequent use of V beta 6/J beta 1.1 in one patient and the V beta 6/J beta 2.7 gene segments in another patient was observed. Regarding the V beta 5.2 transcripts, obtained from the other two patients, no preferential usage of specific J beta gene segments by TIL was observed. These results suggest that the unique T cell populations are amplified in patients with oral SCC, possibly as a consequence of an in situ immune reaction.

In the labial salivary glands (LSGs) of 16 primary and 18 secondary Sjögren's syndrome (SS) patients, infiltrating lymphocytes were histologically and immunohistochemically examined; also, the serum levels of rheumatoid factor, antinuclear antibodies, anti-DNA antibodies, anti-SS-A and anti-SS-B antibodies, and immunoglobulins (including IgG, IgM and IgA) were all assayed. An immunohistochemical analysis of the lymphocyte subsets in LSGs revealed that severe lymphocytic infiltration was frequently accompanied by marked B cell accumulation both in primary and secondary SS patients. Furthermore, local B cell accumulation was also closely associated with elevated levels of anti-SS-A and anti-SS-B antibodies and IgG, and this association was statistically significant in the group with primary SS but not in the group with secondary SS. Thus, local lymphocytic infiltration, especially B cell accumulation, in the salivary glands is suggested to be involved in serological abnormalities in primary SS, while complicated autoimmune diseases other than SS may also be involved in serological abnormalities in secondary SS.