A two-hit mechanism triggers autoimmune hair loss.

Transient depletion of T reg cells during the hair's anagen phase triggers autoimmune hair loss in mice, with 100% developing alopecia under these conditions.

• Why it matters: Understanding how immune tolerance breaks down to cause tissue-specific autoimmunity is crucial for developing targeted treatments for autoimmune diseases like alopecia.
• What they did: The study used mouse models to deplete T reg cells specifically during the anagen phase, revealing that sympathetic nerve activity and ERV reactivation are key factors in initiating autoimmune attack on hair follicle stem cells.
• The result: Findings demonstrate that sympathetic signaling and ERV activation create a vulnerable epithelial state, which, if unchecked by T reg cells, leads to autoimmune hair loss, offering potential therapeutic targets.