Follicular helper T cells may play an important role in the severity of primary Sjögren's syndrome

• Increased percentages of TFH cells are associated with the severity of pSS.
• TFH cell percentages correlates with the enhanced counter-regulatory activity.
• TFH cell percentages correlates with certain B cell subsets and autoantibody levels.
• IL-12 and IL-21 have an important role in immune processes regulated by TFH cells.

The aim of this study was to investigate the possible role of follicular helper T (TFH) cells in the pathogenesis of primary Sjögren's syndrome (pSS) by analyzing immune-competent cells and serological markers with special emphasis on clinical symptoms. We enrolled 50 pSS patients and 16 healthy individuals in the study. Patients had elevated ratio of peripheral TFH cells, however, when dividing patients into two groups defined by the presence of extraglandular manifestations (EGMs), only patients with EGMs differed from controls significantly. Moreover, TFH cell percentages correlated positively with both activated T cell and Tr1 cell values. On the contrary, TFH cell percentages showed negative correlation with both IgM and IgG memory B cell proportions. Elevated TFH percent\ages were observed in the anti-SSA/SSB positive patients, and also in patients with higher IL-12, IL-21 levels and focus score values. Increased TFH cell proportions seem to have an important role in disease development.