Pathogenic Th17 Cells, CD8+CD69+CD49a- Tissue-Resident Memory T Cells, and Common γ Chain Receptor+ Natural Killer Cells Express More IL-17 Compared to IFN-γ Under the Foxp3+ Memory Regulatory T Cells-Depleted Microenvironment in Patients with Chronic Alopecia Areata

This study investigates the role of different immune cells in the pathogenesis of chronic alopecia areata (AA), focusing on tissue-resident memory T cells (TRMs) and memory regulatory T cells (mTregs). The research found that a decrease in Foxp3+ Tregs correlates with increased severity of AA lesions, with cytotoxic T cells and CD8+CD69+CD49a- TRM cells contributing to chronic AA under the influence of mTregs. IL-17 expression was more prominent than IFN-γ in severe AA cases, suggesting IL-17's significant role in AA pathogenesis. The study highlights the insidious destruction of hair follicle stem cells by Th17 lymphocytes and cytotoxic T cells, leading to severe hair loss in chronic AA patients.