It has long been demonstrated that a subset of patients with Sjogren's syndrome 
(SS) develop ectopic lymphoid structures (ELS) in the salivary glands (SG). 
These structures are characterised by periductal clusters of T and B 
lymphocytes, development of high endothelial venules and differentiation of 
follicular dendritic cells (FDC) networks. Evidence in patients with and animal 
models of SS demonstrated that the formation and maintenance of ELS in the SG is 
critically dependent on the ectopic expression of lymphotoxins (LT) and lymphoid 
chemokines CXCL13, CCL19, CCL21 and CXCL12. Several cell types, including 
resident epithelial, stromal and endothelial cells as well as different subsets 
of infiltrating immune cells, have been shown to be capable of producing some of 
these factors during chronic inflammation in SS. In this review we focus on the 
cellular and molecular mechanisms regulating the formation of ELS in SS SG, with 
particular emphasis on the role of lymphoid chemokines. In addition, we 
summarise accumulating data in support of the notion that ELS in SS represent 
functional niches whereby autoreactive B cells undergo affinity maturation, 
clonal selection and differentiation into autoantibody producing cells, thus 
contributing to autoimmunity over and above secondary lymphoid organs. 
Furthermore, we review the emerging role of ELS and lymphoid chemokines in 
driving extranodal B cell lymphomagenesis in SS and we focus on recent evidence 
suggesting that ELS identify subsets of SS patients at increased risk of 
developing systemic manifestations and lymphoma.