Foxp3+ Treg control allergic skin inflammation by restricting IFN-γ-driven neutrophilic infiltration and NETosis

Abstract

Background: Atopic dermatitis (AD), a chronic inflammatory skin disease with T cell activation as a key feature, in which Th2 cell-mediated responses play a pivotal role. Regulatory T cells (Treg) are central immune cells that restrict autoimmunity and inflammation in the body. Patients with immune dysregulation, polyendocrinopathy, or enteropathy X-linked syndrome, an immune disease characterized by a deficiency in Treg, develop skin inflammation and allergic disorders, indicating that Treg play a crucial role in the development of allergic skin inflammation. Objective: we investigated the underlying mechanisms by which Treg control cutaneous allergic inflammation. Methods: An allergic skin inflammation mouse model was constructed using MC903, and Treg-depleted mouse model was constructed using diphtheria toxin. Neutralization of IFN-gamma was constructed using antimouse-IFN-gamma mouse antibody. Neutrophil infiltration was analyzed by flow cytometry and immunohistochemistry. Neutrophil extracellular traps (NETs), a process called NETosis, were detected using immunofluorescence. In vitro neutrophil stimulation and immunocytochemistry was conducted to demonstrate the effect of IFN-gamma on NETosis. Results: The depletion of Foxp3 + Treg led to significantly exacerbated AD-like skin inflammation, including increased recruitment of neutrophils and expression of Th1 cytokine IFN-gamma. Neutrophil infiltrating in skin of Treg-depleted mice released more NETs than wild type. Neutralization of IFN-gamma abolished neutrophil infiltration and NETosis in Treg-depleted mice. Neutrophils stimulated with IFN-gamma were more prone to release NETs in vitro . Finally, Foxp3 + Treg control cutaneous allergic inflammation by regulating IFN-gamma-driven neutrophilic infiltration and NETosis. Conclusion: Our results highlight the previously underestimated Treg-IFN-gamma-neutrophil inflammatory axis. (c) 2024 Japanese Society for Investigative Dermatology.