Introduction
Primary sjögren’s syndrome (pSS) is a typical autoimmune disorder characterized by focal lymphocytic infiltrations, damage, and dysfunction in salivary and lacrimal glands [1]. Lung, kidney, and nervous system involvement could also occur in severe cases [2]. Previous studies have demonstrated the type I IFN signatures in peripheral blood mononuclear cells (PBMCs), B cells, monocytes, neutrophils as well as the affected tissues [3-10]. Moreover, IFN-α inducible proteins: MDA-5, IFIT-3 [11], and B cell-activating factor (BAFF) [12] were found highly expressed in salivary glands. Type I IFN could enhance T cell and B cell responses and promote the production of autoantibodies [11, 13], implicating their important roles in the pathogenesis of pSS.
Acting as a premier type I IFN producer and a key bridge between innate and adaptive immunity, pDCs also play a nonnegligible contribution to autoimmune disease development. pDCs in SLE patients can be activated through various pathways (immune complexes, neutrophil extracellular traps, mitochondrial DNA, etc .), which in turn trigger immune responses and promote the production of autoantibodies [14]. In studies of systemic sclerosis (SSc) [15], Psoriasis [16], rheumatoid arthritis [17] and autoimmune diabetes [18], pDCs could infiltrate into the target tissue and exacerbate local inflammation by releasing IFN-α and proinflammatory factors.
Currently, studies on the role of pDCs in pSS are limited. Previous studies have reported the reduced frequencies of pDCs in peripheral blood [19, 20] of pSS patients. A recent study performed a transcriptional analysis of circulating pDCs and identified the aberrant activation of pDC in pSS patients [21]. Here, we systematically study the percentage, phenotype, and functions of pDCs for a better understanding of their roles in the pathogenesis and type I IFN signatures in pSS patients.