Pathogenesis of primary Sjögren's syndrome beyond B lymphocytes

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder affecting exocrine glands of the body, prevalently lacrimal and salivary glands. The pSS pathogenesis has been thought to be B-cell-centric and several clinical trials have been carried out in order to clarify the therapeutic role of B-cell depletion in patients with pSS. Unfortunately, however, B-cell depletion with rituximab has failed in demonstrating any significant results in pSS patients. Besides the contribution of B cells in the pathogenesis of pSS, effector Tfh, Th17 and Th22 cells, follicular dendritic cells (DCs), innate cells (ICs) and several cytokines, chemokines and miRNA have been proved to participate to the development of this systemic disease. Understanding these molecular processes may help guide research into resistant diseases and highly targeted therapeutic strategies. This review aims to discuss important pathogenetic mechanisms involved in the initiation and perpetuation of pSS behind the established role of B cells.