Association between T follicular helper cells and T peripheral helper cells with B-cell biomarkers and disease activity in primary Sjögren syndrome.

### Key messages #### What is already known about this subject? #### What does this study add? #### How might this impact on clinical practice? Primary Sjogren syndrome (pSS) is a systemic autoimmune disease, characterised by an infiltration of the exocrine glands, leading to sicca syndrome. Extraglandular systemic involvements (such as pulmonary, renal or neurological involvement) occur in about 30% of the patients. One of the most severe complications is the development of B cell lymphoma.1 pSS is characterised by chronic B cell activation, as evidenced by the presence of anti-SSA (Sjogren syndrome A antigen), anti-SSB (Sjogren syndrome B antigen) antibodies, rheumatoid factor (RF) and hypergammaglobulinaemia.2 Using mass cytometry (CyTOF), we have shown an expansion of plasma cells in minor salivary gland and an expansion of circulating plasmablasts in pSS patients, compared with controls.3 Ectopic germinal centres (EGC) in minor salivary glands are present in about one-quarter of the patients and could enhance local production of autoantibodies. T cells also participate to the pathophysiology of pSS, as suggested by the presence of a T lymphocyte infiltrate within the patients' minor salivary gland biopsies,4 as well as the association of pSS with several HLA class II alleles.5 In addition, there is an association between pSS and a single-nucleotide polymorphisme located within CXCR5 locus that codes for a key chemokine expressed by T follicular helper (Tfh) cells. Tfh are a subset of T lymphocytes specialised in providing help to B cells, and are essential for EGC formation, recruitment (via CXCL13) …