[The clinical significance of circulating follicular helper T cells in patients with anti-neutrophil cytoplasmic myeloperoxidase antibody-associated vasculitis].

To investigate the change of circulating follicular helper T cells (cTfh) in patients with anti-neutrophil cytoplasmic myeloperoxidase antibody-associated vasculitis (MPO-AAV), and to analyze the relationship between cTfh and disease activity. Thirty-eight untreated MPO-AAV patients (patient group) and thirty-eight healthy volunteers (control group) were enrolled in this study. cTfh and membrane expression of inducible co-stimulator (ICOS) and programmed cell death protein 1 (PD-1) were detected by flow cytometry (FCM). Serum anti-neutrophil cytoplasmic myeloperoxidase antibody (MPO-ANCA) was measured by ELISA. Disease activity was evaluated by Birmingham vasculitis activity score (BVAS). Compared with those in control group, the proportions of cTfh, ICOS(+)Tfh and PD-1(+) Tfh cells in patient group were significantly higher [(25.9±3.8)% vs. (21.0±5.3)%, <0.001; (1.8±0.8)% vs. (0.8±0.5)%, <0.001 and (10.2±2.8)% vs. (8.2±2.2)%, 0.001, respectively]. Meanwhile, the expression of ICOS and PD-1 on cTfh in patient group was markedly more intensive (59.6±10.0 vs.49.2±6.9, <0.001 and 532.6±104.2 vs. 485.1±73.4, 0.025, respectively). In patient group, the proportion of cTfh was positively correlated with the ratio of ICOS(+)Tfh, the expression of ICOS, the level of MPO-ANCA and BVAS (0.407, 0.011; 0.705, 0.001; 0.737, 0.001 and 0.663, 0.001, respectively). The expression intensity of ICOS on cTfh was positively associated with ICOS(+)Tfh ratio, serum MPO-ANCA and BVAS (0.388, 0.016; 0.645, 0.001 and 0.653, 0.001, respectively). Nevertheless, the expression of PD-1 on cTfh was only positively correlated with the ratio of PD-1(+) Tfh (0.473, 0.003). Enhanced cTfh in patients with MPO-AAV might produce MPO-ANCA, which is related to the aggravation of MPO-AAV. Thus, cTfh and its ICOS could be potentially targeted for the treatment of MPO-AAV.