CD4(-)CD8(-) T-cells in primary Sjögren's syndrome: association with the extent of glandular involvement.

Abstract Objectives Growing evidence suggests that IL-17-producing T cells, lacking both CD4 and CD8 molecules and defined as double negative (DN) cells, play a pivotal role in the pathogenesis of a number of systemic autoimmune disorders. We recently demonstrated that this T-cell subset is expanded in the peripheral blood (PB) of patients with primary Sjogren's syndrome (pSS), produces IL-17 and accumulates in minor salivary glands (MSGs). We aimed to investigate glandular and PB DN T cells in early pSS in order to verify a possible correlation with MSGs histological patterns and clinical parameters. Methods Paired samples of PB mononuclear cells and MSGs from pSS patients were evaluated at the diagnosis by flow cytometry and immunofluorescence staining respectively. Histological analysis to identify histological scores, B/T cell segregation and the presence of germinal center (GC)-like structures was also performed. Results In early stages of pSS, circulating DN T cells appear to be not yet expanded and inversely correlated with circulating CD4 + Th17 cells. The number of infiltrating DN T cells were associated with extent of glandular involvement, presence of GC-like structures and dryness symptoms and were inversely correlated with circulating DN T cells. Conclusions Our findings suggest that DN T cells are actively involved in the pathogenic mechanisms leading to glandular dysfunction and damage in pSS and may play a role in ectopic lymphoneogenesis development occurring during the disease.