Objective. To study the effects of a novel A-type retrovirus, detected in cocultures of lip biopsy specimens from Sjogren'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