Increased peripheral helper T cells type 17 subset correlates with the severity of psoriasis vulgaris

•Phenotype of Tph17 cells is activated and proliferative in psoriasis vulgaris.•Tph17 cells and plasma CXCL13 could be biomarkers for evaluating the severity of psoriasis vulgaris.•Tph17 cells and the CXCL13/CXCR5 axis might represent new immunotherapeutic targets for psoriasis vulgaris. Recently, a new subgroup of T cells, named peripheral helper T (Tph) cells, has been implicated in autoimmune pathogenesis. An imbalance of Tph cell subsets influences the severity of immune-related diseases. However, the characteristics and roles of Tph cell subsets in psoriasis remain unknown. Programmed cell death 1-positive, chemokine C-X-C receptor (CXCR) 5-negative Tph cells can be divided into 3 subgroups based on differential expression of chemokine CXCR3 and chemokine C-C receptor (CCR) 6. CXCR3+CCR6− Tph cells are classified as Tph1, CXCR3−CCR6− Tph cells are classified as Tph2, and CXCR3−CCR6+ Tph cells are classified as Tph17. In this study, conditions of circulating Tph cell subsets and CD4+CXCR5+ follicular helper T (Tfh) cells in 27 patients with psoriasis and 13 healthy individuals were detected by flow cytometry. The level of plasma chemokine C-X-C ligand (CXCL) 13 was measured by enzyme-linked immunosorbent assay. The correlations between the above indexes and disease severity were explored. In the peripheral blood of patients with psoriasis, Tph17 cells had an activated, proliferative phenotype; the quantity of the cells correlated with disease severity. Plasma CXCL13 levels were elevated in psoriasis and associated with disease severity and the frequency of Tph17 cells. CD4+CXCR5+ Tfh cells were increased in patients and positively correlated with disease severity, the frequency of Tph17 cells, and plasma CXCL13 levels. Our results suggest that Tph17 cells and the CXCL13/CXCR5 axis may be involved in the pathogenesis of psoriasis and represent new immunotherapeutic targets for treating psoriasis.