In the salivary glands of primary Sjögren's syndrome (pSjS) patients, type I IFN activity is increased, but systemic levels of type I IFN proteins are rarely detected. This study focused on the systemic activity of type I IFN in pSjS, as well as the role of peripheral plasmacytoid dendritic cells (pDC). Monocytes obtained from pSjS patients showed an increased expression of 40 genes. Twenty-three of these genes (58%), including IFI27, IFITM1, IFIT3 and IFI44, were inducible by type I IFN. pSjS serum had an enhanced capability of inducing IFI27, IFITM1, IFIT3 and IFI44 in the monocytic cell line THP-1, likely due to the action of IFN-β. This effect could be inhibited by blocking the type I IFN receptor, supporting a high type I IFN bioactivity in pSjS serum. In addition, circulatory pDC showed increased expression of CD40. This expression was correlated to the expression level of the type I IFN-regulated genes IFI27 and IFITM1 in monocytes of the same individual. This study indicates that the increased type I IFN activity observed in pSjS patients is not only a local but also a systemic phenomenon and points to pDC as a possible source of this activity.

Plasmacytoid DC, Sjögren's syndrome, Type I interferon,
European Journal of Immunology
Erasmus MC: University Medical Center Rotterdam

Wildenberg, M.E, van Helden-Meeuwsen, C.G, van de Merwe, J.P, Drexhage, H.A, & Versnel, M.A. (2008). Systemic increase in type I interferon activity in Sjögren's syndrome: A putative role for plasmacytoid dendritic cells. European Journal of Immunology, 38(7), 2024–2033. doi:10.1002/eji.200738008