IL-17-producing CD4-CD8- T cells are expanded in the peripheral blood, infiltrate salivary glands and are resistant to corticosteroids in patients with primary Sjogren's syndrome.

Objectives: It has been recently observed that a T-cell subset, lacking of both CD4 and CD8 molecules and defined as double negative (DN), is expanded in the blood of patients with systemic lupus erythematosus, produces IL-17 and accumulates in the kidney during nephritis. Since IL-17 production is enhanced in salivary gland infiltrates of primary Sjögren's syndrome (SS) patients, we investigated whether DN T cells may be involved in the pathogenesis of salivary gland damage.

Methods: Phenotypic characterisation of peripheral blood mononuclear cells from SS patients and controls was performed by flow cytometry in freshly isolated and anti-CD3-stimulated cells. SS minor salivary glands were processed for immunofluorescence staining.

Results: CD3(+)CD4(-)CD8(-) DN T cells were major producers of IL-17 in SS and expressed ROR-γt. They were expanded in the peripheral blood, spontaneously produced IL-17 and infiltrated salivary glands. In addition, the expansion of αβ-TCR(+) DN T cells was associated with disease activity. Notably, IL-17-producing DN T cells from SS patients, but not from healthy controls, were strongly resistant to the in vitro effect of dexamethasone.

Conclusions: These findings appear to be of great interest since the identification of a peculiar T-cell subset with pro-inflammatory activity, but resistant to corticosteroids, in an autoimmune disorder such as SS may help to design new specific treatments for the disease.