Chemokine CXCL13 facilitates anti-FVIII inhibitory antibody development in hemophilia A patients and murine models.

The development of anti-factor VIII (FVIII) neutralizing antibodies (inhibitors) remains challenging complication in hemophilia A (HA) patients undergoing prophylactic FVIII replacement therapy. The pathogenesis of FVIII inhibitor formation remains unclear. Chemokine CXCL13, a key ligand for follicular helper T cells (TFHs), in the context of inhibitor development were assessed in the present study. A total of 113 HA patients, with and without inhibitors, along with 72 healthy volunteers, were enrolled. Results demonstrated abnormally elevated levels of CXCL13 in HA patients, with a 2.0-fold increase in patients with inhibitors compared to those without. Similarly, CXCL13 levels were significantly elevated in both wild-type and HA mice with FVIII inhibitors. The proportions of circulating and splenic TFHs were markedly higher in inhibitor patients and murine models and positively correlated with CXCL13 levels. Moreover, plasma levels of B cell activating factor and the inflammatory biomarker HMGB1 were significantly increased in both human and animal inhibitor cohorts. An increased frequency of germinal center B cells was observed in splenocytes from inhibitor mice. In vitro study revealed human dermal microvascular endothelial cells undergoing immunogenic ferroptosis when conditioned with high levels of CXCL13, which was associated with down-regulation of ferroptosis suppressors SLC7A11 and GPX4, activation of the Nrf2 pathway, and increased intracellular reactive oxygen species. The findings of this study suggest that CXCL13 play a pivotal role in the microenvironment of anti-FVIII antibody development. Targeting CXCL13 may offer a potential therapeutic approach for FVIII inhibitors in HA.