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

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.