Clinical significance of circulating follicular helper T cells in patients with idiopathic membranous nephropathy

Objective  To explore the expression characteristics of follicular helper T cells （Tfh） and its subsets in peripheral blood of patients with idiopathic membranous nephropathy （IMN）, examine the relationship between Tfh cells and IMN and understand the clinical significance of circulating follicular helper T cells in IMN patients.

Methods  A total of 41 new-onset IMN patients from January 2020 to December 2020 were recruited as IMN group while 30 healthy volunteers from medical examination center as healthy control group. The frequency of Tfh cell and its two cell subsets of ICOS⁺ Tfh and PD-1⁺ Tfh were examined by flow cytometry. The serum level of IL-21 was measured by enzyme-linked immunosorbent assay （ELISA）; The expression of IL-21 in Tfh cells was analyzed by reverse transcription-polymerase chain reaction （RT-PCR）. Clinical data of two groups were collected from electronic medical record system of our hospital. ResultsAs compared with healthy control group, the frequency of Tfh cell and its cell subsets ICOS⁺ Tfh and PD-1⁺ Tfh and ratio of ICOS⁺/PD-1⁺ Tfh cell rose markedly in peripheral blood of IMN patients. A higher serum level of IL-21 and frequency of Tfh cell were correlated positively with serum level of IL-21. The expression of IL-21 was up-regulated in Tfh cell. Ratio of ICOS⁺/PD-1⁺ Tfh cell was correlated positively with serum level of IgG4. The frequency of Tfh cell in peripheral blood was correlated positively with 24 h urinary protein.

Conclusion  Follicular helper T cells are involved in immune disorder of IMN patients. Tfh cells become hyperfunctional. And the frequency of Tfh cells may be a new indicator for assessing the disease development of IMN.