Signal transduction in Sjögren's syndrome T cells. Abnormalities associated with a newly described human A‐type retrovirus

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Abstract
Objective. To study the effects of a novel A‐type retrovirus, detected in cocultures of lip biopsy specimens from Sjögren's syndrome (SS) patients and a human T cell line, on the infected T cells. Methods. Interleukin‐2 (IL‐2) and IL‐6 secretion were measured by bioassay and enzyme‐linked immunosorbent assay, respectively, in the infected and noninfected cell lines. Surface antigen expression was determined by flow cytometry, using monoclonal antibodies. Protein kinase C (PKC) activity was measured using an enzyme assay kit, and calcium mobilization was assessed with a fluorescent probe. Results. Infected cells expressed less CD4 and IL‐6 receptor, but more HLA‐DR, compared with noninfected cells. Infected cells also produced less IL‐2 and displayed reduced PKC activation and calcium mobilization. A similar defect in calcium mobilization was detected in T cells from SS patients. Conclusion. These data suggest a possible involvement of the newly described retrovirus in T cell abnormalities.