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High frequency of circulating follicular helper T cells is correlated with B cell subtypes in patients with ankylosing spondylitis.

T follicular helper (Tfh) cells are known to support effector B cells and enhance autoimmunity; however, the association between the Tfh cells and B cells in ankylosing spondylitis (AS) is unclear. The aim of the present study was to measure the frequency of circulating cluster of differentiation (CD)4+ C-X-C chemokine receptor type 5 (CXCR5)+ Tfh cells and B cell subtypes in peripheral blood from patients with AS, and evaluate the correlation of these factors. Percentages of peripheral blood circulating CD4+CXCR5+ Tfh cells and B cell subtypes were measured via flow cytometry and the disease activity of individual patients was measured using the Bath AS Disease Activity Index (BASDAI). The potential association among these measures was analyzed via Spearman's or Pearson's correlations. In comparison with those in healthy controls (HC), significantly increased percentages of CD4+CXCR5+ cTfh, CD4+CXCR5+ programmed death 1+, CD4+CXCR5+ inducible T cell costimulator (ICOS)+, CD3+CD8-CXCR5+ interleukin (IL)-21+ T cells, CD19+CD27high plasmablast and CD19+CD38+ antibody-secreting B cells were detected in patients with AS, whereas there was no significant difference in CD19+CD27- naïve B cells and CD19+CD27+ memory B cells. When Patients with AS were divided into high and low activity groups, significantly higher percentages of CD4+CXCR5+, CD3+CD8-CXCR5+IL-21+ T cells, CD19+CD27- naïve B cells and CD19+CD38+ antibody-secreting B cells, and lower CD19+CD27+ memory B cells were detected in high activity AS group compared with the low activity AS group. In addition, percentages of CD4+CXCR5+ circulating (c)Tfh, CD3+CD8-CXCR5+IL-21+ T and CD19+CD38+ antibody-secreting B cells were positively correlated with BASDAI values. Furthermore, the percentage of CD4+CXCR5+ cTfh cells was positively correlated with CD19+CD38+ antibody-secreting B cells and the percentage of CD3+CD8-CXCR5+IL-21+ T cells was positively correlated with CD19+CD27- naïve B cells in patients with AS. These findings suggest that CD4+CXCR5+ cTfh, CD3+CD8-CXCR5+IL-21+ T and CD19+CD38+ antibody-secreting B cells may participate in the pathogenesis of AS because of their distinct functions. As such, levels of cTfh and B cell subtypes may be a useful biomarker for the evaluation of disease activity in patients with AS.