Increased CD4<sup>+</sup>CXCR5<sup>+</sup>T follicular helper cells in diabetic nephropathy

<p><i>Background</i>: T follicular helper (Tfh) cells are known to regulate humoral immune response. In this study we examined the correlation of different subsets of peripheral blood Tfh cells in patients with diabetic nephropathy (DN). <i>Methods</i>: A total of 23 DN patients and 15 healthy controls (HC) were investigated for various subsets of Tfh cells by flow cytometry. The molecules ICOS<sup>+</sup>, PD-1<sup>+</sup>, CD28<sup>+</sup>, CD154<sup>+</sup>, IL-21<sup>+</sup>, IFN-γ<sup>+</sup>, IL-4<sup>+</sup>, IL-17<sup>+</sup> Tfh cells were examined. The subsets of B cells were investigated by flow cytometry. The levels of 24 h urinary protein and estimated glomerular filtration rate (eGFR) were calculated. A potential correlation between the number of different subsets of Tfh cells, B cells and DN, was assessed. <i>Results</i>: The circulating CD4<sup>+</sup>CXCR5<sup>+</sup>PD-1<sup>+</sup>, PD-1<sup>+</sup>CD154<sup>+</sup>, PD-1<sup>+</sup>CD28<sup>+</sup>, PD-1<sup>+</sup>IL-21<sup>+</sup>, PD-1<sup>+</sup>IL-4<sup>+</sup>, PD-1<sup>+</sup>-IL-17<sup>+</sup>-Tfh cell counts, CD38<sup>+</sup>CD19<sup>+</sup>, CD38<sup>+</sup>CD19<sup>+</sup>CD40<sup>+</sup> B cells and plasma levels of IL-21 were significantly increased in DN patients (<i>p</i> < 0.05), as compared to that in the HC group. Furthermore, the circulating CD4<sup>+</sup>CXCR5<sup>+</sup>PD-1<sup>+</sup> Tfh cell counts negatively correlated with eGFR; Tfh cell counts positively correlated with 24 h urinary protein concentration in DN patients. Post-treatment, there was a significant reduction in the CD4<sup>+</sup>CXCR5<sup>+</sup>PD-1<sup>+</sup> Tfh cell counts and its subsets, with a corresponding decrease in plasma levels of IL-6 and IL-17A (<i>p</i> < 0.05) in DN patients, as compared to the HCs. <i>Conclusion</i>: An increased number of CD4<sup>+</sup>CXCR5<sup>+</sup>PD-1<sup>+</sup> Tfh cells were observed in DN patients, which may be new targets for intervention in DN.</p>